The Role of Dna Technology in Crime Investigation Essay Example

The Role of Dna Technology in Crime Investigation Essay Example The Role of Dna Technology in Crime Investigation Essay The Role of Dna Technology in Crime Investigation Essay DNA profiling DNA profiling (also called DNA testing, DNA typing, or genetic fingerprinting) is a technique employed by forensic scientists to assist in the identification of individuals on the basis of their respective DNA profiles. DNA profiles are encrypted sets of numbers that reflect a persons DNA makeup, which can also be used as the persons identifier. DNA profiling should not be confused with full genome sequencing. It is used in, for example, parental testing and rape investigation. Although 99. 9% of human DNA sequences are the same in every person, enough of the DNA is different to distinguish one individual from another.DNA profiling uses repetitive (repeat) sequences that are highly variable called variable number tandem repeats (VNTR). VNTRs loci are very similar between closely related humans, but so variable that unrelated individuals are extremely unlikely to have the same VNTRs. The DNA profiling technique was first reported in 1984by Sir Alec Jeffreys at the Univer sity of Leicester in England, and is now the basis of several national DNA databases. Dr. Jeffreyss genetic fingerprinting was made commercially available in 1987, when a chemical company, ICI, started a blood-testing center in England.DNA profiling process The process begins with a sample of an individuals DNA (typically called a reference sample). The most desirable method of collecting a reference sample is the use of a buccal swab, as this reduces the possibility of contamination. When this is not available (e. g. because a court order may be needed and not obtainable) other methods may need to be used to collect a sample of blood, saliva, semen, or other appropriate fluid or tissue from personal items (e. g. toothbrush, razor, etc. ) or from stored samples (e. g. banked sperm or biopsy tissue).Samples obtained from blood relatives (biological relative) can provide an indication of an individuals profile, as could human remains which had been previously profiled. A reference sam ple is then analyzed to create the individuals DNA profile using one of a number of techniques, discussed below. The DNA profile is then compared against another sample to determine whether there is a genetic match. * RFLP analysis The first methods for finding out genetics used for DNA profiling involved restriction enzyme digestion, followed by Southern blot analysis.Although polymorphisms can exist in the restriction enzyme cleavage sites, more commonly the enzymes and DNA probes were used to analyze VNTR loci. However, the Southern blot technique is laborious, and requires large amounts of undegraded sample DNA. Also, Karl Browns original technique looked at many minisatellite loci at the same time, increasing the observed variability, but making it hard to discern individual alleles (and thereby precluding parental testing). These early techniques have been supplanted by PCR-based assays. PCR analysis With the invention of the polymerase chain reaction (PCR) technique, DNA prof iling took huge strides forward in both discriminating power and the ability to recover information from very small (or degraded) starting samples. PCR greatly amplifies the amounts of a specific region of DNA, using oligonucleotide primers and a thermostable DNA polymerase. Early assays such as the HLA-DQ alpha reverse dot blot strips grew to be very popular due to their ease of use, and the speed with which a result could be obtained.However they were not as discriminating as RFLP. It was also difficult to determine a DNA profile for mixed samples, such as a vaginal swab from a sexual assault victim. Fortunately, the PCR method is readily adaptable for analyzing VNTR loci. In the United States the FBI has standardized a set of 13 VNTR assays for DNA typing, and has organized the CODIS database for forensic identification in criminal cases. Similar assays and databases have been set up in other countries. Also, commercial kits are available that analyze single-nucleotide polymorphi sms (SNPs).These kits use PCR to amplify specific regions with known variations and hybridize them to probes anchored on cards, which results in a colored spot corresponding to the particular sequence variation. * STR analysis The method of DNA profiling used today is based on PCR and uses short tandem repeats (STR). This method uses highly polymorphic regions that have short repeated sequences of DNA (the most common is 4 bases repeated, but there are other lengths in use, including 3 and 5 bases).Because unrelated people almost certainly have different numbers of repeat units, STRs can be used to discriminate between unrelated individuals. These STR loci (locations on a chromosome) are targeted with sequence-specific primers and amplified using PCR. The DNA fragments that result are then separated and detected using electrophoresis. There are two common methods of separation and detection, capillary electrophoresis (CE) and gel electrophoresis. Each STR is polymorphic, however, th e number of alleles is small. Typically each STR allele will be shared by around 5 20% of individuals.The power of STR analysis comes from looking at multiple STR loci simultaneously. The pattern of alleles can identify an individual quite accurately. Thus STR analysis provides an excellent identification tool. The more STR regions that are tested in an individual the more discriminating the test becomes. From country to country, different STR-based DNA-profiling systems are in use. In North America, systems which amplify the CODIS 13 core loci are almost universal, while in the UK the SGM+ system (which is compatible with The National DNA Database), is in use.Whichever system is used, many of the STR regions used are the same. These DNA-profiling systems are based on multiplex reactions, whereby many STR regions will be tested at the same time. The true power of STR analysis is in its statistical power of discrimination. Because the 13 loci that are currently used for discriminati on in CODIS are independently assorted (having a certain number of repeats at one locus doesnt change the likelihood of having any number of repeats at any other locus), the product rule for probabilities can be applied.This means that if someone has the DNA type of ABC, where the three loci were independent, we can say that the probability of having that DNA type is the probability of having type A times the probability of having type B times the probability of having type C. This has resulted in the ability to generate match probabilities of 1 in a quintillion (1 with 18 zeros after it) or more. However, DNA database searches showed much more frequent than expected false DNA matches including one perfect 13 locus match out of only 30,000 DNA samples in Maryland in January 2007.Moreover, since there are about 12 million monozygotic twins on Earth, that theoretical probability is useless. For example, the actual probability that 2 random people have the same DNA depends on whether t here were twins or triplets (etc. ) in the family, and the number of loci used in the test. Where twins are common, the probability of matching the DNA is 22 in 1000, or about 2. 2 in 100 will have matching DNA. In practice, the risk of contaminated-matching is much greater than matching a distant relative, such as a sample being contaminated from nearby objects, or from left-over cells transferred from a prior test.Logically, the risk is greater for matching the most common person in the samples: everything collected from, or in contact with, a victim is a major source of contamination for any other samples brought into a lab. For that reason, multiple control-samples are typically tested, to ensure that they stayed clean, when prepared during the same period as the actual test samples. Unexpected matches (or variations) in several control-samples indicates a high probability of contamination for the actual test samples.In a relationship test, the full DNA profiles should differ (e xcept for twins), to prove that a person wasnt actually matched as being related to their own DNA in another sample. * AmpFLP Another technique, AmpFLP, or amplified fragment length polymorphism was also put into practice during the early 1990s. This technique was also faster than RFLP analysis and used PCR to amplify DNA samples. It relied on variable number tandem repeat (VNTR) polymorphisms to distinguish various alleles, which were separated on a polyacrylamide gel using an allelic ladder (as opposed to a molecular weight ladder).Bands could be visualized by silver staining the gel. One popular locus for fingerprinting was the D1S80 locus. As with all PCR based methods, highly degraded DNA or very small amounts of DNA may cause allelic dropout (causing a mistake in thinking a heterozygote is a homozygote) or other stochastic effects. In addition, because the analysis is done on a gel, very high number repeats may bunch together at the top of the gel, making it difficult to resol ve. AmpFLP analysis can be highly automated, and allows for easy creation of phylogenetic trees based on comparing individual samples of DNA.Due to its relatively low cost and ease of set-up and operation, AmpFLP remains popular in lower income countries. DNA family relationship analysis Using PCR technology, DNA analysis is widely applied to determine genetic family relationships such as paternity, maternity, siblingship and other kinships. During conception, the father’s sperm cell and the mother’s egg cell, each containing half the amount of DNA found in other body cells, meet and fuse to form a fertilized egg, called a zygote.The zygote contains a complete set of DNA molecules, a unique combination of DNA from both parents. This zygote divides and multiplies into an embryo and later, a full human being. DNA does not change once it is formed at conception. At each stage of development, all the cells forming the body contain the same DNA- half from the father and hal f from the mother. This fact allows the relationship testing to use all types of all samples including loose cells from the cheeks collected using buccal swabs, blood or other types of samples.While a lot of DNA contains information for a certain function, there is some called junk DNA, which is currently used for human identification. At some special locations (called loci) in the junk DNA, predictable inheritance patterns were found to be useful in determining biological relationships. These locations contain specific DNA markers that DNA scientists use to identify individuals. In a routine DNA paternity test, the markers used are Short Tandem Repeats (STRs), short pieces of DNA that occur in highly differential repeat patterns among individuals.Each person’s DNA contains two copies of these markers- one copy inherited from the father and one from the mother. Within a population, the markers at each person’s DNA location could differ in length and sometimes sequence, depending on the markers inherited from the parents. The combination of marker sizes found in each person makes up his/her unique genetic profile. When determining the relationship between two individuals, their genetic profiles are compared to see if they share the same inheritance patterns at a statistically conclusive rate.For example, the following sample report from this commercial DNA paternity testing laboratory Universal Genetics signifies how relatedness between parents and child is identified on those special markers: |DNA Marker |Mother |Child |Alleged father | |D21S11 |28, 30 |28, 31 |29, 31 | |D7S820 |9, 10 |10, 11 |11, 12 | |TH01 |14, 15 |14, 16 |15, 16 | |D13S317 |7, 8 |7, 9 |8, 9 |D19S433 |14, 16. 2 |14, 15 |15, 17 | The partial results indicate that the child and the alleged father’s DNA match among these five markers. The complete test results show this correlation on 16 markers between the child and the tested man to draw a conclusion of whether or not the man is the biological father. Scientifically, each marker is assigned with a Paternity Index (PI), which is a statistical measure of how powerfully a match at a particular marker indicates paternity.The PI of each marker is multiplied with each other to generate the Combined Paternity Index (CPI), which indicates the overall probability of an individual being the biological father of the tested child relative to any random man from the entire population of the same race. The CPI is then converted into a Probability of Paternity showing the degree of relatedness between the alleged father and child. The DNA test report in other family relationship tests, such as grandparentage and siblingship tests, is similar to a paternity test report. Instead of the Combined Paternity Index, a different value, such as a Siblingship Index, is reported.The report shows the genetic profiles of each tested person. If there are markers shared among the tested individuals, the probability of biological relationship is calculated to determine how likely the tested individuals share the same markers due to a blood relationship. * Y-chromosome analysis Recent innovations have included the creation of primers targeting polymorphic regions on the Y-chromosome (Y-STR), which allows resolution of a mixed DNA sample from a male and female and/or cases in which a differential extraction is not possible.Y-chromosomes are paternally inherited, so Y-STR analysis can help in the identification of paternally related males. Y-STR analysis was performed in the Sally Hemings controversy to determine if Thomas Jefferson had sired a son with one of his slaves. * Mitochondrial analysis For highly degraded samples, it is sometimes impossible to get a complete profile of the 13 CODIS STRs. In these situations, mitochondrial DNA (mtDNA) is sometimes typed due to there being many copies of mtDNA in a cell, while there may only be 1-2 copies of the nuclear DNA.Forensic scientists amplify the HV1 and HV2 regions of the mtDNA, then sequence each region and compare single-nucleotide differences to a reference. Because mtDNA is maternally inherited, directly linked maternal relatives can be used as match references, such as ones maternal grandmothers daughters son. A difference of two or more nucleotides is generally considered to be an exclusion. Heteroplasmy and poly-C differences may throw off straight sequence comparisons, so some expertise on the part of the analyst is required. tDNA is useful in determining clear identities, such as those of missing people when a maternally linked relative can be found. mtDNA testing was used in determining that Anna Anderson was not the Russian princess she had claimed to be, Anastasia Romanov. mtDNA can be obtained from such material as hair shafts and old bones/teeth.. DNA databases There are now several DNA databases in existence around the world. Some are private, but most of the largest databases are government controlled. The United States maintains the largest DNA database, with the Combined DNA Index System, holding over 5 million records as of 2007.The United Kingdom maintains the National DNA Database (NDNAD), which is of similar size, despite the UKs smaller population. The size of this database, and its rate of growth, is giving concern to civil liberties groups in the UK, where police have wide-ranging powers to take samples and retain them even in the event of acquittal. The U. S. Patriot Act of the United States provides a means for the U. S. government to get DNA samples from other countries if they are either a division of, or head office of, a company operating in the U. S.Under the act, the American offices of the company cant divulge to their subsidiaries/offices in other countries the reasons that these DNA samples are sought or by whom. When a match is made from a National DNA Databank to link a crime scene to an offender who has provided a DNA Sample to a databank that link is often referred to as a cold hit. A cold hit is of value in referring the police agency to a specific suspect but is of less evidential value than a DNA match made from outside the DNA Databank. Considerations when evaluating DNA evidenceIn the early days of the use of genetic fingerprinting as criminal evidence, juries were often swayed by spurious statistical arguments by defense lawyers along these lines: given a match that had a 1 in 5 million probability of occurring by chance, the lawyer would argue that this meant that in a country of say 60 million people there were 12 people who would also match the profile. This was then translated to a 1 in 12 chance of the suspect being the guilty one. This argument is not sound unless the suspect was drawn at random from the population of the country.In fact, a jury should consider how likely it is that an individual matching the genetic profile would also have been a suspect in the case for other reasons. Another spurious statistical argument is based on the false assumption that a 1 in 5 million probability of a match automatically translates into a 1 in 5 million probability of innocence and is known as the prosecutors fallacy. When using RFLP, the theoretical risk of a coincidental match is 1 in 100 billion (100,000,000,000), although the practical risk is actually 1 in 1000 because monozygotic twins are 0. % of the human population. Moreover, the rate of laboratory error is almost certainly higher than this, and often actual laboratory procedures do not reflect the theory under which the coincidence probabilities were computed. For example, the coincidence probabilities may be calculated based on the probabilities that markers in two samples have bands in precisely the same location, but a laboratory worker may conclude that similar- but not precisely identical- band patterns result from identical genetic samples with some imperfection in the agarose gel.However, in this case, the laboratory worker increases the coincidence risk by expanding the criteria for declaring a match. Recent studies have quoted relatively high error rates which may be cause for concern. In the early days of genetic fingerprinting, the necessary population data to accurately compute a match probability was sometimes unavailable. Between 1992 and 1996, arbitrary low ceilings were controversially put on match probabilities used in RFLP analysis rather than the higher theoretically computed ones. Today, RFLP has become widely disused due to the advent of more discriminating, sensitive and easier technologies.STRs do not suffer from such subjectivity and provide similar power of discrimination (1 in 10^13 for unrelated individuals if using a full SGM+ profile) It should be noted that figures of this magnitude are not considered to be statistically supportable by scientists in the UK, for unrelated individuals with full matching DNA profiles a match probability of 1 in a billion is considered statistically supportable (Since 1998 the DNA pr ofiling system supported by The National DNA Database in the UK is the SGM+ DNA profiling system which includes 10 STR regions and a sex indicating test.However, with any DNA technique, the cautious juror should not convict on genetic fingerprint evidence alone if other factors raise doubt. Contamination with other evidence (secondary transfer) is a key source of incorrect DNA profiles and raising doubts as to whether a sample has been adulterated is a favorite defense technique. More rarely, chimerism is one such instance where the lack of a genetic match may unfairly exclude a suspect. Evidence of genetic relationship Its also possible to use DNA profiling as evidence of genetic relationship, but testing that shows no relationship isnt absolutely certain.While almost all individuals have a single and distinct set of genes, rare individuals, known as chimeras, have at least two different sets of genes. There have been several cases of DNA profiling that falsely proved that a mother was unrelated to her children. Fake DNA evidence The value of DNA evidence has to be seen in light of recent cases where criminals planted fake DNA samples at crime scenes. In one case, a criminal even planted fake DNA evidence in his own body: Dr. John Schneeberger raped one of his sedated patients in 1992 and left semen on her underwear.Police drew what they believed to be Schneebergers blood and compared its DNA against the crime scene semen DNA on three occasions, never showing a match. It turned out that he had surgically inserted a Penrose drain into his arm and filled it with foreign blood and anticoagulants. In a study conducted by the life science company Nucleix and published in the journal Forensic Science International, scientists found that an In vitro synthesized sample of DNA matching any desired genetic profile can be constructed using standard molecular biology techniques without obtaining any actual tissue from that person.Development of artificial DNA In August 2 009, scientists in Israel stunned the forensic sciences and raised serious questions concerning the use of DNA by law enforcement as the ultimate method of identification. In a paper published in the journal Forensic Science International: Genetics, the Israeli researchers demonstrated that it is possible to manufacture DNA in a laboratory, and thus falsify DNA evidence. The scientists fabricated saliva and blood samples, which originally contained DNA from a person other than the ostensible donor of the blood and saliva.The researchers also showed that, using a DNA database, it is possible to take information from a profile and manufacture DNA to match it, and that this can be done without access to any actual DNA from the person whose DNA they are duplicating. The synthetic DNA oligos required for the procedure are common in molecular laboratories. Dr. Daniel Frumkin, lead author on the paper, was quoted in The New York Times as saying, You can just engineer a crime scene any biol ogy undergraduate could perform this. Dr.Frumkin perfected a test that can forensically differentiate real DNA samples from fake ones. His test uses epigenetic modifications, in particular, DNA methylation. Seventy percent of the DNA in any human genome is methylated, meaning it contains methyl group modifications within a CpG dinucleotide context. Methylation at the promoter region is associated with gene silencing. The synthetic DNA lacks this epigenetic modification, which allows the test to distinguish manufactured DNA from original, genuine, DNA.It is unknown how many, if any, police departments currently use the test, which appears to be a serious issue in light of Frumkin’s claim that the DNA manufacturing procedure is within the grasp of any undergraduate biology student. No police lab has publicly announced that it is using the new test to verify DNA results, while FSI Genetics says that any forensic laboratory doing DNA identification should adopt this test to auth enticate its results as real DNA. Cases In the 1950s, Anna Anderson claimed that she was Grand Duchess Anastasia Nikolaevna of Russia; in the 1980s after her death, samples of her tissue that had been stored at a Charlottesville, Virginia hospital following a medical procedure were tested using DNA fingerprinting and showed that she bore no relation to the Romanovs. In 1986, Richard Buckland was exonerated despite having admitted to the rape and murder of a teenager near Leicester, the city where DNA profiling was first discovered. This was the first use of DNA finger printing in a criminal investigation. In 1987 it was the first time genetic fingerprinting was used in criminal court where a man accused of unlawful intercourse with a mentally handicapped 14-year-old female who gave birth to his baby. In 1987, in the same case as Buckland, British baker Colin Pitchfork was the first criminal caught and convicted using DNA fingerprinting In 1987, Florida rapist Tommy Lee Andrews was t he first person in the United States to be convicted as a result of DNA evidence, for raping a woman during a burglary; he was convicted on 6 November 1987 and sentenced to 22 years in prison. In 1988, Timothy Spencer was the first man in Virginia to be sentenced to death through DNA testing, for several rape and murder charges; he was dubbed The South Side Strangler because he killed victims on the southside of Richmond, Virginia. He was later charged with rape and 1st degree murder and was sentenced to death. He was executed on April 27, 1994. David Vasquez, initially convicted of one of Spencers crimes, became the first man in America exonerated based on DNA evidence. In 1992, DNA evidence was used to prove that Nazi doctor Josef Mengele was buried in Brazil under the name Wolfgang Gerhard. The Role of the Forensic Geneticist Forensic genetics is the study of DNA characteristics and patterns. The scientific knowledge base of a forensic geneticist can have different applications i n fields such as law enforcement and anthropology. One of the functions of a forensic geneticist is to examine and profile DNA evidence from a crime scene in order to determine the presence of a suspect.In another discipline such as anthropology, the geneticist may study historical human migration patterns by comparing DNA in diverse racial groups. Because DNA marking and profiling has a small margin of error, its results can be questioned. * Criminal Forensics All DNA contains sequences of nucleotides which have a unique recurring pattern for each person. A forensic geneticist first obtains a sample of DNA from a sample of tissue, bodily fluid or hair. The repeating nucleotide sequences found in the sample are then cut with specialized proteins and isolated.The sample is then probed by special DNA molecules which have been extracted from a known donor. If the probe DNA matches the sample nucleotides collected from a crime scene, then it theoretically places the donor at the scene i tself. * Victim Identification DNA can also be used to identify human remains where decomposition has left the body unrecognizable, or where dental records do not exist. Typically DNA from the unknown remains is matched with a sample of verified DNA from a missing person, or can be compared against possible family members.Genetic matching are also tools in paternity tests. Forensic Genetics has also been employed in identifying victims of war crimes located in mass graves. * Forensic Anthropology One of the most recent fields in anthropology has been the study of ancient human migrations. Using mitochondrial DNA (which is only passed down through the mother) and Y-chromosomal DNA (inherited through the father) forensic geneticists have been able to chart the course of human migrations out of the Africa over the last 60,000 years.This is accomplished by examining mutations of the two kinds of DNA, which occur rarely and only over an average number of generations. The divergence of mu tations in different existing ethnic groups can be compared and a rough chronological and geographical chart of migration is then laid out. * Accuracy in Criminal Investigation Findings by an Arizona crime lab analyst suggest that even if an overall DNA profile is unique to an individual, certain portions of it are similar to family members, and possibly (by coincidence) to unrelated individuals.This has the potential to challenge the widespread belief that DNA profiling is a foolproof tool in criminal investigations. Doubts can potentially be raised about whether a DNA profile for a suspect really belongs to that individual. How genetic engineering or DNA technology may help in crime investigation? agriculture? and medicine? DNA technology can help with crime investigation to help find a criminal who has left bodily fluid at a crime scene. They use DNA tests to find a match. Genetic engineering can be used in agriculture to create a crop that is superior to other crops.It can make a plant stronger and larger, etc. Genetic engineering in medicine is being used to help a couple who is trying to have a baby. If the one of the parents has a disease (such as Huntingtons, Parkinsons, etc. ) to create a baby that doesnt have the disease. The children are called designer babies. Law the Genetics of Identity: The Science of DNA Fingerprinting New Noteworthy, 2007 In Law and The Genetics of Identity, The DNA Files looked at DNA forensics, privacy and the law.There are many ways in which experts use genetic techniques for identification purposes, from identifying missing persons to solving criminal investigations. DNA evidence arguably has become the best-known type of forensic evidence, made more recognizable by popular television programs (including three CSIs and four Law Orders). Although the forensic tools used on TV allow detectives to solve horrendous crimes in under an hour, real-life techniques do require a few days. A DNA profile is a composite of about 13 areas of highly variable short tandem repeats (STRs) that characterize each individual.While humans share a vast majority of our DNA sequence with one another, some sections of our non-coding DNA are unique. Using DNA profiling techniques, it is possible to establish a likely match. The International Commission on Missing Persons (ICMP) was created in 1996 as a result of the conflicts related to Bosnia-Herzegovina, the Republic of Croatia, and Republic of Serbia from 1991 to 1995. The ICMP uses DNA as a means to identify victims of war atrocities and natural disasters. As of April 2006, the ICMP had helped identify 902 people who had died in the 2004 South Asian tsunami.In 2005, the ICMP partnered with Louisiana health officials to perform DNA tests on 256 bone samples from Katrina victims. Forensic specialists created DNA profiles from these bone samples then sent the data to Louisiana authorities for matching with family members DNA samples there. In recent years, researchers and policing organizations also have made significant inroads in criminal investigation methods. New forensic polymerase chain reaction (PCR), STR, and mtDNA techniques have sped up analysis of a DNA profile extracted from crime scene evidence.What once took between 6 and 8 weeks now takes between 1 and 2 days. Scientists hope that someday it will take only a few hours to generate a DNA profile from a sample. According to President George W. Bushs DNA Initiative in 2003, one of the biggest problems facing the criminal justice system today is the substantial backlog of unanalyzed DNA samples and biological evidence from crime scenes, especially in sexual assault and murder cases. Timely analysis of these samples can help police arrest and detain potentially violent offenders or solve no-suspect cases.While timely analysis is important, identifying the correct person is even more important. Opponents of DNA profiling point out that case-specific issues and problems often damage the quali ty and relevance of DNA test results. The increased use of genetic technologies in crime investigation has contributed to many forensic databases, including two run by the Federal Bureau of Investigation: the Automated Fingerprint Identification System, which catalogs millions of fingerprints, and the Combined DNA Index System (CODIS).CODIS was once reserved for those convicted of violent offenses, but the 2004 Justice for All Act expanded the database so states can now upload profiles of almost anyone charged with any crime. In 2006, the FBI opened its DNA database to kinship DNA matching. A DNA sample from a crime scene that fails to be an exact match to any profile in a forensic database can now be used to find possible relatives that are in the database. Opponents fear that partial matches violate protection by the U.S. Constitution against unreasonable search and seizure and undermine the principle of presumptive innocence. Genetic techniques can also be used to exonerate a per son convicted of a crime. As of October 2007, the Innocence Project, founded by Barry C. Scheck and Peter J. Neufeld at the Benjamin N. Cardozo School of Law at Yeshiva University in New York, had helped exonerate 208 people in the United States using DNA testing, including 15 who served time on death row.Byron Halsey, for instance, who narrowly escaped the death penalty when he was convicted in 1988 of the brutal sexual assault and murder of two young children in New Jersey, was fully exonerated in July 2007 based on DNA evidence. DNA can also help bring closure to cases that have gone cold. In 2006, after almost 30 years of dead ends, investigators in Virginia used carefully preserved blood taken from a 1977 crime scene in order to identify and arrest a suspect in the killing of Henry William Long.Questions surrounding the social, ethical, and legal issues of using genetic technologies in crime investigation persist. In a few cases, geographic and ethnic genetic testing have been applied to criminal investigations to help narrow the suspect search field. Critics fear that the information gathered and stored in this type of testing could be used for research on topics such as the genetic correlates of ethnicity or criminal behavior, fueling flawed science and dangerous prejudices. These

Expert Guide to the ACT Format What You Need to Know

Expert Guide to the ACT Format What You Need to Know SAT / ACT Prep Online Guides and Tips If you want to do well on the ACT, it’s not enough to just study test content. You have to know the test inside and out, including what questions to expect, what reading passages to anticipate, and what topic areas you’ll encounter the most. Being this familiar with the test will help you improve your score in a significant way - it’s much more effective than just focusing on test content. In this post, I’ll go over everything you need to know about how the ACT is written, including format, content, and question types. At the end, I’ll tell you exactly what you can do to successfully incorporate this knowledge into your ACT study plan. Why Is Familiarity With the ACT Format Helpful? The ACT is an incredibly predictable test. Although there have been a few recent changes, the test format has (in general) stayed pretty consistent over the past few decades. This works to your advantage for a few very important reasons: Familiarity with the test helps you focus on, and improve on, your weaknesses. The ACT is super predictable when it comes to test content and format, down to the number of questions that test a certain concept. If you’re familiar with the test format and structure as you study, you can narrow your focus to very specific question types and content areas that may be bringing down your score. It helps you improve your ACT strategy, which is just as important as preparing for test content. The ACT writes the test sections, questions, and answer choices in a very particular and consistent style. Familiarizing yourself with the basic structure and format of the ACT is like getting to know the test inside-out - if you can get inside the mind of a test writer, you’ll have a huge advantage on the test. The more experience you have with this style, the better you’ll be able to anticipate which answers are correct and incorrect on test day It helps you work on time management, an important part of succeeding on any standardized test. Knowing the general layout of the test, in addition to knowing what your own strengths and weaknesses are, is an integral part of ACT time management. If you can’t finish the questions on time, you won’t do well, no matter how well you know the material. Finally, the fewer surprises you encounter on test day, the better. When you know exactly what to expect when you take the ACT, you can focus on the most important part of the test: demonstrating what you know in order to get a great score. Knowing the test format and structure inside and out may help alleviate test-taking anxiety, a verycommon problem that impacts many students’ scores. The Basics: The Structure of the ACT The ACT has four mandatory multiple-choice sections which are always presented in the same order: (1) English, (2) Math, (3) Reading, and (4) Science. There’s also an optional (5) Writing section for a total of five test sections. The total test time without the Writing section is 2 hours and 55 minutes. The total test time with the Writing section is 3 hours and 35 minutes. Here’s what you can expect in terms of number of questions, time limit, time per question, and question type for each of the ACT sections: English Number of questions 75 Time limit 45 minutes Approximate time per question 36 seconds Question type Multiple choice with four answer choices Math Number of questions 60 Time limit 60 minutes Approximate time per question 1 minute Question type Multiple choice with five answer choices Reading Number of questions 40 Time limit 35 minutes Approximate time per question 52 seconds Question type Multiple choice with four answer choices Science Number of questions 40 Time limit 35 minutes Approximate time per question 52 seconds Question type Multiple choice with four answer choices Writing Number of questions 1 Time limit 40 minutes Approximate time per question 40 minutes Question type Essay prompt Content and Skills: What Does the ACT Test? The next step in familiarizing yourself with the ACT is knowing exactly what concepts, skills, and content will be tested on the exam. If you know what content will appear, and you know exactly how it will be tested, all of your bases will be covered (remember, the fewer the surprises on test day, the more you can focus on what’s important). The ACT is pretty transparent about test content. Here, I’ll go over what you’ll need to prepare for each section and what these sections will actually look like. English On this section you’ll be presented with passages. You’ll either have to choose the correct version of a sentence within the passage or will have to answer more broad questions about the construction of the passage itself (you’ll see a couple examples shortly). The ACT English section tends to heavily favor a few main grammar and style rules, and just lightly touches on the other minor ones. This means (unless you’re aiming for a very high score), you can focus primarily on these main rules as you prepare for the test. There are two main types of English questions: ones that test usage and/or mechanics, and ones that test rhetorical skills. Below you’ll find approximate breakdowns for the number of each question type you’ll see on the test. When it comes to Usage and Mechanics (about 40 out of a total of 75 questions), the main grammar rules tested on the ACT are: Correctly forming and joining sentences (20.5% of grammar questions) Correct use of commas, dashes, and colons (17.7% of grammar questions) Correctly using nonessential clauses and relative pronouns (9.6% of grammar questions) Correct verb tense and form (9.6% of grammar questions) When it comes to Rhetorical Skills (about 30 out of a total of 75 questions), the main rhetorical rules tested on the ACT are: Logical transitions (18% of rhetorical questions) Adding information (16.7% of rhetorical questions) Conciseness (15.5% of rhetorical questions) Replacing and re-wording information (15.5% of rhetorical questions) Most of the questions on ACT English test this content by asking you to choose the most correct version of a sentence within a passage - you’ll have to choose among four answer choices in this section. For example: A question where you choose the correct version of a sentence. Some questions are formatted a bit differently, and instead ask you about a passage as a whole. For example: For more information on this section, check out our ultimate ACT English prep guide. Math The math section is a little different from other ACT sections. Some math questions are stand-alone - they won’t be linked to any other questions in the section - whereas others are linked â€Å"sets.† You’ll have to choose from five multiple-choice responses instead of four (which obviously makes things more difficult). Math questions are also roughly arranged in order of difficulty. You can generally split the section into three zones: Questions 1-20: Easy Questions 21-40: Medium Questions 41-60: Hard Difficulty is determined by the amount of time you’ll need to solve a problem, the number of steps required, the number of math concepts you must employ, and the likelihood that you’ll be familiar with the material. Learn about how to take advantage of this organization of question by difficulty. Because they’re arranged by difficulty, these questions are also roughly arranged by content, with â€Å"easier† math concepts (i.e. ones you’ve spent more years studying) at the beginning of the section and â€Å"hard† concepts (i.e. ones you’re less familiar with) at the end. Generally, you’ll see more algebra questions toward the beginning and more geometry and trig toward the end of any ACT math section. Here’s a breakdown of the topics you’ll see on ACT math for a general overview: Pre-algebra: about 20-25% of questions Elementary algebra: about 15-20% of questions Intermediate algebra: about 15-20% of questions Coordinate geometry: about 15-20% of questions Plane geometry: about 20-25% of questions Trigonometry: about 5-10% of questions Read our more detailed guide to ACT math content for more information. Now, on to some examples. Most questions on this section are stand-alone questions, meaning they’re in no way related to any other question on the section. A stand-alone question may look like this: You might see some sets of math questions on the ACT where two or more questions are related to each other, or refer to the same figure. Here’s an example of what a prompt like that would look like: For more information on this section, check out our ultimate ACT math prep guide. Reading The ACT Reading test is made up of four different subsections. Each of these subsections has either one long passage or two shorter, paired passages. In this section, every question will ask you to respond to or interpret the passages. The Reading section will present you with one reading passage for each subsection, and the types of passages you’ll see will always be in the same order: Prose Fiction/Literary Narrative Social Science Humanities Natural Science The ACT tests this content with a variety of question types. Fortunately, we have a general idea of how often each question type shows up on the average Reading section - with this information, you can think more critically about question types that you may need to spend more time preparing. Here’s a typical section breakdown by question type: Question Type Average Number of Questions Percentage of Questions Big Picture 4 10% Little Detail 18 45% Vocabulary in Context 3 8% Development and Function 9 22% Inference 6 15% All Questions 40 100% The info above isn’t helpful if you can’t identify the sorts of questions you’ll see on the Reading section, right? Here are the main question types you’ll see on the English section, followed by examples: Big Picture - Deal with the main point of the passage or the narrator’s overall point of view. These types of questions require you to look at the passage holistically rather than focusing on one specific section. Little Picture/Detail - Ask about a small piece of factual information in a passage. They are the most straightforward questions because they’re so literal - you just have to find the correct information. Vocabulary in Context - Ask about the meaning of a word in the context of the passage. They may also reference something in the passage and ask you to choose a vocabulary word that best describes it. Development and Function - Ask about how a certain paragraph, sentence, or phrase functions in the context of the passage, how the argument in the passage was developed, or how the author structured the passage. Inference - Ask you to make inferences based on a logical extension of information found in a passage. Check out our guide to ACT Reading questions for more detailed information and examples. Science The ACT Science section consists of several â€Å"passages† where you’ll have to respond to short paragraphs, charts, graphs, tables, or some combination thereof - they’re not like the passages in the Reading section where you just respond to a wall of text. All of these passages are just different ways of presenting data for you to interpret. Because of the way the section is formatted, you’ll see sets of questions, like you sometimes see on Math, rather than stand-alone questions. The passages themselves may be on a variety of topics, including: Biology Chemistry Earth/space sciences Physics Just like with the Reading section, it’s not necessary for you to have specific background knowledge in these topic areas - you just need the skills to interpret the passages correctly. There are three main passage formats. Each format will present data in a different way - a set of multiple-choice questions after each passage will ask you to interpret and/or analyze this information. Here’s what to expect for each format: Format #1: Data Representation This format presents one or more sets of data in some sort of graphical representation. What you’re asked to do: understand, evaluate, and interpret information presented in graphs, tables, or charts Number of questions: About 15 (38% of total ACT Science questions) Here’s what a â€Å"passage† may look like in a Data Representation format: And here’s what a multiple-choice question may look like in response to the Data Representation format: Passage Format #2: Research Summaries This format presents the results of two or more experiments, usually with text in addition to graphs or charts. What you’re asked to do: understand, evaluate, and analyze one or more experiments Number of questions: About 18 (45% of total ACT Science questions) Here’s what a â€Å"passage† may look like in a Research Summaries format: Here’s what a multiple-choice question may look like in response to the Research Summaries format: Passage Format #3: Conflicting Viewpoints This format presents several different conflicting scientific hypotheses, usually in a text passage. What you’re asked to do: understand and evaluate conflicting viewpoints, theories, or hypotheses on a specific topic Number of questions: About 7 (17% of total ACT Science questions) Here’s what a â€Å"passage† may look like in a Conflicting Viewpoints format: Here’s what a multiple-choice question may look like in response to the Conflicting Viewpoints format: For more information and example questions on the ACT Science section, check out our ultimate prep guide. Writing The ACT Writing section is completely optional - that being said, I’d encourage you to do some research before deciding not to take it (as tempting as that may be)! Students have 40 minutes to plan, write, and edit an essay in response to one writing prompt. Prompts tend to address contemporary issues (e.g. the pros and cons of living in an increasingly automated society). So what exactly do these prompts look like? Well, students are provided with three diverse perspectives on a particular issue. After reading these perspectives, students are asked to develop their own take on the topic and explain the relationships between the original perspectives. Put simply, your jobs are to: Take a position on a topic (and defend it) Address all the diverse perspectives presented to you Explain the relationships between those three perspectives Here’s an example of what an ACT writing prompt looks like: Check out our complete guide to ACT writing and scoring for more information. Using ACT Formatting: How to Prep for the ACT Earlier in this post, I mentioned that familiarizing yourself with the ACT format can help you in a few important areas: Identifying your weaknesses Coming up with a strategic game plan Improving time management Alleviating stress that comes with surprises on test day Here, I’ll address exactly what you can do (in all four of these areas) to use knowledge of ACT format and structure to your advantage. Identify Your Weaknesses When you know exactly what will be tested on the ACT, and exactly how it will be tested, you can use your practice materials to hone in on sections, content areas, question types, and passage types that give you more trouble than others. This strategy only works if you invest a significant amount of time in working through and then analyzing ACT practice materials. Official ACT practice tests are the best for this - ideally, you’ll down under realistic testing conditions with an official practice test to get a baseline score. As you work through your practice material, keep careful track of where you’re losing points - doing a post-mortem on your work is the most important thing you can do to improve your score. I’d encourage you to set up a spreadsheet for easy mistake tracking. For each ACT practice section, for example, you’ll want to ask yourself: Which questions am I getting wrong? Which types of questions am I getting wrong? Do I lose more points on a particular type of passage? (E.g. perhaps Research Summary passages in ACT Science give you a hard time) Do I lose points at the end of a section because I run out of time? Do I lose points in a particular content/knowledge set area? (E.g. maybe you have trouble with absolute value in ACT math) Come Up With a Strategic Game Plan Once you have a better idea of where you need to improve, you can come up with an ACT study plan that’s catered to your weaknesses. If you have a baseline score, you’ll have a sense of how many points you’d like to bring your score up. Here’s a general guideline for how long you need to study based on your improvement goals: 0-1 ACT Composite Point Improvement: 10 hours 1-2 ACT Point Improvement: 20 hours 2-4 ACT Point Improvement: 40 hours 4-6 ACT Point Improvement: 80 hours 6-9 ACT Point Improvement: 150 hours+ Read more about putting together a study plan that works for you. Improve Time Management If you know what to expect on the ACT, you’ll be better able to work through the test on the fly. If you know what slows you down (e.g. a particular question type or content area) you can plan on doing speed drills during practice or skipping (and then returning) to those questions on the test. For example, reading passages - like the ones you’ll find in ACT Science and ACT Reading - tend to slow down a lot of students. If you know that this is a personal sore spot, you should read our guides to time management on ACT Science and ACT Reading. If you have an idea of what to expect, you’ll be that much better at navigating the stressful time limits of the test. Alleviate Stress Coming up against unexpected obstacles - especially when you’re in a time crunch - is pretty stressful for most people. By engaging in regular practice with official ACT prep materials, you’re doing yourself a huge favor by taking the stress of unexpected content and formatting out of the equation. For more info on alleviating stress, read our guide on what to expect and how to prepare for the ACT test day. What’s Next? Now that you have all this great information about the ACT and how it’s structured, you might be interested in learning more about some other logistical issues - like how it’s scored. Read first about the scoring system with our complete guide to ACT scores. Then, figure out what target score you should be aiming for. For expert tips, read our famous guide on how to get a perfect score on the ACT. Want to improve your ACT score by 4 points? Check out our best-in-class online ACT prep classes. We guarantee your money back if you don't improve your ACT score by 4 points or more. Our classes are entirely online, and they're taught by ACT experts. 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