DNA Testing

2012-06-13 12:55:44

Deoxyribonucleic acid, or DNA, is the genetic information contained within the nucleus of cells. It is found in all living cells in the body and determines how the body grows and develops; it is essentially a recipe book for life. DNA controls inherited characteristics, such as the color of one’s eyes and hair. DNA is made up of many millions of pieces of discrete information and their exact combination in any person is unique except for identical twins, who share the same DNA. DNA Testing, sometimes called DNA profiling or fingerprinting, does not examine a person’s entire DNA; instead, it focuses on a few highly variable components of the genetic code. This means that a DNA test gives a probability that two samples with the same genetic components come from the same person, a related person, or an unrelated person.

The techniques behind DNA Testing were first developed in the United Kingdom by Sir Alec Jeffreys at the University of Leicester in 1984. Professor Jeffreys was a microbiologist studying inherited genetic variations between people. While he was examining the human myoglobin gene, he noticed what he called a ‘‘minisatellite’’—a small sequence of DNA that was repeated many times and was theoretically open to a number of slight variations due to mutation and replication. By using these minisatellites as landmarks, Jeffreys was able to find and analyze systematically the differences in people’s DNA.

Collection of DNA Evidence

DNA evidence can be recovered from a wide variety of cells and is very easily left behind at a crime scene. It can be recovered from buccal cells found in saliva, from semen, blood, or even from hair follicles. DNA can also be preserved for a long time, and some tests have been performed on remains that are hundreds of years old. The collection of DNA for testing can be a painless and comparatively nonintrusive process using a mouth swab or a hair, but most states in the USA require a blood sample to be drawn.

DNA Testing in the Courtroom

The world’s first use of DNA Testing in court was in a British immigration case in 1985 to determine the identity of a young boy. The boy in question had been born in the United Kingdom and was the son of British citizens of Ghanaian extraction. He traveled to Ghana and, upon his return, his passport was rejected as a possible forgery. The courts had to determine whether he was the boy in the passport or some other relative from Ghana. The family’s lawyer asked Jeffreys for help and he was able to develop a genetic ‘‘fingerprint’’ that proved the boy was who his family said he was. Testing is frequently used in this way to determine paternity in cases where that is disputed.

The world’s first application of DNA profiling in a criminal case also took place in the United Kingdom, in 1986. In that case two young girls had been raped and murdered three years apart, but the cases were similar enough that police suspected that they were victims of the same man. The police arrested someone who confessed to the second murder, but not the first, and asked Jeffreys to compare forensic evidence gathered from the two cases with those of the man in custody. The DNA profile showed that the same man was responsible for both murders, but that the man who had confessed was not that person. The police collected DNA samples from over five thousand local men and ultimately used the DNA evidence in the successful prosecution of the murderer, who tried to avoid detection by sending a friend to give a DNA sample in his place. DNA profiling first appeared in a courtroom in the United States in State of Florida v. Tommy Lee Andrews, 533 So. 2d 841 (Fla. Dist Ct. App 1988), and helped to convict Andrews of rape.

DNA Dragnets

As its name suggests, a DNA dragnet involves requesting a DNA sample from a large number of people in the hopes of obtaining a sample that matches one recovered from a crime scene. If the sample does not match, the police can eliminate that person from their inquiries, though police can become suspicious if a person refuses to give a sample. There is usually some attempt to target a particular subsection of the public—for example, local males within a particular age range and/or of a particular race—but this still encompasses a great many people.

In the United States a DNA dragnet can be particularly controversial because it is generally held that the Fourth Amendment protects one from ‘‘mass suspicionless searches’’ (Veronia School Dist. v. Acton, 94-590, 515 U.S. 646, 1995). Moreover, the idea that refusing to give a DNA sample might make the police more suspicious seems to defeat the spirit of the law’s presumption of innocence. Problems can also arise depending upon the manner of the police in collecting samples. There have been a number of instances in the United States where DNA dragnets have been used, and people have subsequently complained that the police pressured them into giving samples and did not make it seem like a voluntary process. These problems have been exacerbated in cases in which a racial group was the target of a dragnet, leading to charges of racism in the execution of the dragnet.

Perhaps the greatest potential concern with DNA dragnets relates to the police use of the sample. Will it be compared only to the sample from the crime that sparked the dragnet or will it also be compared against samples recovered from other, unrelated crime scenes? Once the sample shows that the person is not connected to this crime, will the sample be destroyed or saved for future use and entered into the DNA database? Most jurisdictions now guarantee that a sample given in a dragnet will be returned or destroyed, along with any record of the DNA profile after it has been compared to the evidence and found not to be a match.

DNA Databases

Police forces rapidly understood the potential for DNA Testing to be a powerful tool for law enforcement. As the techniques to analyze DNA became more sophisticated, faster, and cheaper, the possibility of creating a DNA database modeled after long established fingerprint databases grew to a reality. DNA samples recovered from a crime scene could be compared against a permanent record of known DNA samples. This created the possibility of suspects being positively identified many years after the offense took place, thus helping to solve so-called cold cases. A standardized repository for DNA evidence would also allow police in different jurisdictions to link crimes committed by the same person. The United Kingdom became the first country in the world to create a national DNA database in 1995. In the United States the Federal Bureau of Investigation’s National DNA Index System became operational in 1998.

Collecting Samples for the DNA Database

Most jurisdictions now have laws mandating DNA Testing and entry into a DNA database. Some limit this to those convicted of crimes such as murder and rape, but the trend has been to expand the range of offenses covered to all felonies, with the aim of constructing a database containing DNA samples from all the ‘‘active criminals’’ within that jurisdiction. Some protest against this as a violation of privacy, but the generally accepted position is that, when one commits a crime, one loses some rights and the collection of DNA from convicted criminals to construct a database is now almost universally accepted.

One problem common during the initial stages of setting up a DNA database and requiring DNA samples to be given was whether such measures could be applied retroactively. Should those already convicted and serving time in prison be required to give samples? Should those released on parole be required to give a DNA sample? While there is still no definitive pronouncement on these matters in the United States, the consensus is that DNA samples can be taken from prisoners, even if their offenses took place before the enabling legislation, and from those convicted afterwards. It can also be a condition of parole to provide a DNA sample, though opinion is divided on the question of whether those already given parole could be forced to give samples if that was not a requirement of their parole, and some jurisdictions have allowed this.

Problems with DNA Databases

Unlike fingerprints, DNA samples contain information that reveals something about the private life of the subject. This raises extra concerns regarding how this information is used.

DNA samples can reveal whether the person has genetic disorders or propensities towards medical conditions that have not yet manifested. This could place the state in a position in which it knows more about the health of the subject than the subject does. Subjects could even find out information about their health from the state that they would rather not have known. This also raises concerns about access to this information, particularly by private companies providing services such as insurance.

One of the biggest differences between the information in fingerprints and DNA tests is whose privacy interests are at stake. Fingerprints are thought to be unique, unrelated to other physical characteristics, and devoid of familial connection. DNA, on the other hand, can be very similar between blood relations. Criminals forfeit some of their privacy when they are convicted of a crime and must submit fingerprints and DNA samples to aid future identification. Their family members have not been convicted of anything, but the state will gain substantial information about them through the sample. In 2004, the United Kingdom saw the world’s first conviction based upon familial DNA in the National DNA Database. Evidence recovered from the scene was almost identical to a sample in the database and police traced the family tree until they found the person responsible. As DNA databases grow in size, such convictions will become more likely in the future, leading some to question whether it is ethical to store and trace DNA information in this way.

Cross-Jurisdictional Issues for DNA Databases

There are concerns about who can have access to a DNAdatabase, especially across jurisdictional boundaries and when one jurisdiction has different standards for collecting and maintaining evidence. For example, one jurisdiction might require samples taken from someone arrested but not convicted of a crime to be destroyed, but another might retain that sample. As the technical sophistication of databases increases and information is shared more across jurisdictions, the problems of differing sensitivities to the privacy considerations will come to the fore, as will the ethical use of information from one jurisdiction that would have been destroyed or never collected in another.

Implications of the Use of DNA Testing

As DNA Testing is becoming more sophisticated and the relationship between genes is better understood, the range of information one can glean from a DNA is growing. DNA can provide information on gender, race, and eye color that could be used in conjunction with traditional policing techniques to link a particular person with a DNA sample. This raises the possibility of increasingly sophisticated DNA ‘‘photofits’’ of the person being sought.

While the extent to which our genetic makeup determines us as individuals is unknown, there is the suggestion that one day everything from eyesight to left handedness to sexual orientation could be revealed by DNA Testing. The sheer range and wealth of information might force a re-examination of the ways with which DNA Testing is dealt.

The potential to use DNA evidence to link people conclusively to crimes committed decades earlier can have a far reaching impact on the calculus to determine the statute of limitations on crimes, especially of a sexual nature. This capacity has led to pressure to extend the timeframe to prosecute in the knowledge that, while witnesses’ memories may deteriorate over time, forensic evidence, if properly tested and stored, can provide reliable evidence for many years to come.

DNA and Innocence

DNA can also be and has been used to show that through a miscarriage of justice, an innocent person has been convicted of an offense. This is troubling for any justice system and all the more so when the person was convicted of a capital crime. The availability of DNA evidence has prompted changes to allow new appeals based on DNA evidence.


References and Further Reading

  • Laurie, Graeme. Genetic Privacy: A Challenge to Medico- Legal Norms. New York: Cambridge University Press, 2002.
  • Lazer, David. DNA and the Criminal Justice System: The Technology of Justice. Boston: MIT Press, 2004.
  • National Conference of State Legislatures. ‘‘DNA and Crime,’’ https://www.ncsl.org/programs/health/genetics/ dna.htm.
  • National Criminal Justice Reference Service. ‘‘What Every Law Enforcement Officer Should Know About DNA Evidence,’’ https://www.ncjrs.org/nij/DNAbro/ intro.html.
  • Rothstein, Mark A., ed. Genetic Secrets: Protecting Privacy and Confidentiality in the Genetic Era. New Haven, CT: Yale University Press, 1999.
  • Tutton, Richard, and Oonagh Corrigan, eds. Genetic Databases: Socio-ethical Issues in the Collection and Use of DNA. New York: Routledge, 2004.

Cases and Statutes Cited

  • State v Andrews, 533 So. 2d 841 (Fla. Dist Ct. App 1988)
  • Vernonia Sch. Dist. 47J v. Acton, (94-590), 515 U.S. 646 (1995)

See also Capital Punishment and Right of Appeal; Cloning; Duty to Obey Court Orders; Right of Privacy; Search (General Definition); Search Warrants; State Constitution, Privacy Provisions