DNA in Criminal Law Overview and Analysis

Subject: Law
Pages: 9
Words: 2294
Reading time:
8 min
Study level: College


This research paper explores core areas in the use of DNA samples in criminal laws. Deoxyribonucleic acid (DNA) is “the primary component for an individual’s entire genetic composition” (James, 2012). Forensic investigators normally analyze obtained DNA sequences (loci) in a crime laboratory. This is critical for creating a profile, which helps in the identification of the suspect. It is not difficult to obtain a DNA sample because the methods are not invasive. Any part of the human body can provide a sample for DNA testing, including a microscopic amount of bodily secretion, fluids, or tissue.

DNA has served as an effective instrument of law enforcement during investigations. Each human being has exceptional DNA composition, with the exception of the same twins. Investigators can obtain DNA from several sources, such as “hair, bone, teeth, saliva, and blood” (James, 2012). In the 1980s, most states in the US enacted laws, which required investigators to “gather DNA samples for criminals found guilty of sexual and other forms of violent crimes” (James, 2012). Investigators analyzed such samples and stored them in the state DNA database.

DNA history

DNA testing has existed since 1985. Testing normally involves the use of biological features like skin, hair, blood, and other bodily fluids (James, 2009). DNA testing has developed to be the most accurate method of obtaining physical evidence against suspects engaged in criminal activities. DNA testing has been effective in cases of sexual assaults. Since DNA makeup is distinct, investigators normally analyze genetic materials at the scene of the crime and link the same with the DNA of the alleged offender. The results are usually 99 percent accurate.

Today, many countries around the world have embraced DNA testing and assembled databases for finding criminals. In the US, the FBI has the DNA data of millions of lawbreakers, particularly in sex offenses and other violent crimes. Most states insist on the submission of DNA testing results to law enforcement agencies.

The accuracy of DNA testing has increased over the years. In addition, the costs of conducting DNA testing have also dropped significantly. These factors have enhanced the use of DNA testing in most areas beyond criminal cases. For instance, DNA testing has become the preferred method of determining paternity through a do-it-yourself test by using easily available test kits from drugstores (James, 2009). Super Bowl footballs have DNA as a way of eliminating “counterfeit ones because it is not simple to match the pigskins’ genetic sequence right” (James, 2009). Scientists have extended the use of DNA testing in identifying human remains in cases of controversies or devastating events, which normally destroy bodies beyond recognition. For instance, after the 9/11 attacks, the US government established a large DNA database for the identification of the victims. In other cases, DNA testing has been instrumental in exonerating convicts, even from death row. By the year 2009, courts had overturned nearly 240 convictions in 33 states and the District of Columbia based on DNA test results. Still, 17 convicts had escaped death row after DNA results proved their innocence. In Argentina’s dirty war, DNA science was critical in most cases.

Where can DNA be found at a crime scene?

Investigators can obtain samples from virtually any place at the crime scene. Imaginative investigators can gather their samples from unfamiliar sources at the crime scene. Some critical sources for DNA samples may include DNA swabbed from cigarette butts, hair, semen, postage stamps, undergarments, dirty laundry, bite marks, used condoms, fingernails, hat, mask, and other items, which the offender may be having at the time of the crime. It is imperative to note that evidence for DNA samples may come from unlikely sources at the crime scene.

How is DNA collected and stored at a crime scene?

Investigators and forensic experts must collaborate to identify the most important pieces of evidence at the crime scene. It is imperative to establish priorities during sample collection and storage at the crime scene. All officers at the crime scene must recognize critical elements involved in the “identification, collection, transportation, and storage of DNA evidence” (National Criminal Justice Reference Service, 1999). Some biological materials may have “dangerous pathogens, including the deadly HIV, and hepatitis B virus” (James, 2012).

DNA samples are sensitive. Thus, they require extreme caution during collection and storage at the crime scene. Investigators and forensic analysts must take precautions not to contaminate small samples when identifying, collecting, and storing obtained DNA evidence.

Contamination of DNA evidence is simple. Sneezing or coughing over the evidence or touching on the mouth, nose, or other parts of the face and then touching areas, which may contain the DNA for testing, automatically contaminate the biological samples (National Criminal Justice Reference Service, 1999). This may lead to complications during testing because the PCR technology just replicates DNA evidence presented for analysis. Thus, contamination and other unintended DNA may implicate people who are not suspects in the case. Officers must avoid contamination of the scene at all costs. It is advisable for officers to wear gloves, clean equipment thoroughly, or use disposable ones for sample collection.

At the same time, storage of DNA samples requires similar precautions. Biological samples should be air-dry prior to wrapping. It is advisable to put evidence into “new paper bags or envelopes, not into plastic bags, and never use staples” (National Criminal Justice Reference Service, 1999).

How is DNA used in criminal investigations?

The federal and state DNA databases have become fundamental in solving criminal cases, eliminating cases of sentencing innocent people, and proving the innocence of people who courts have erroneously convicted. Criminal investigators have used DNA evidence to solve criminal cases in the following ways. First, in a situation where officers have identified a suspect, forensic experts can “analyze and compare DNA samples with the biological samples from the crime scene” (James, 2012). The result could show that the suspect either committed the crime or was at the scene of the crime. Second, in a situation where officers have not identified a suspect, “forensic experts can analyze biological evidence from the crime scene and make a comparison against a suspect’s DNA profile in the DNA databases” (James, 2012). This helps in the identification of offenders. In addition, forensic investigators have also used biological evidence from a certain crime scene and linked them with evidence from other crime scenes in order to show that they originated the same suspect.

The establishment of DNA databases

The federal law allows the Federal Bureau of Investigation (FBI) to “establish and run a national DNA database” (James, 2012). These DNA databases have DNA profiles, which originate from a suspect in crimes and people who may give samples under certain legal conditions. Samples from crime scenes are useful in generating criminal leads during investigations.

The law also grants authority to officers to gather DNA samples from arrestees and federal criminals. In addition, they can also gather DNA samples from military suspects and other suspects from the District of Columbia.

State law shows criminals who must provide their DNA samples for databases. However, the federal law clarifies the type of DNA profiles for the state database and the national DNA database.

Requirements for DNA Accreditation

The FBI selects DNA profiles for the Combined DNA Index System (CODIS) based on 13 main loci. These 13 main loci are critical in ensuring that all forensic laboratories can have the same DNA databases in order to facilitate sharing of forensic data by the National DNA Index System (NDIS). The current 13 loci do not reflect human attributes like “height, eye or skin color, or susceptibility to a particular disease” (James, 2012). Thus, the 13 loci are non-coding. These 13 loci provide high standards of discriminatory power.

Some states require forensic laboratories to obtain accreditation. Most public laboratories have accreditation. The main body that accredits almost all laboratories is the American Society of Crime Laboratory Directors/Laboratory Accreditation Board ASCLD/LAB. In addition, most laboratories under special grants must also operate within the FBI’s QAS. FBI requires yearly auditing of laboratories to ensure that they operate within the QAS guidelines. Moreover, forensic analysts must also undertake proficiency tests within the year.

All forensic laboratories must adhere to commonly accepted standards, practices, and procedures as provided by accreditation bodies or other certifying organizations. Accreditation also ensures that most forensic laboratories qualify for grants and funds from different sources.

However, forensic laboratories may not be free of errors. Accreditation shows that forensic laboratories have the best practices throughout all states.

Oversight and Reporting on Forensic Practices

Some states have bodies, which report and make recommendations about forensic practices. This aims at improving the quality of forensic services. Other states have forensic commissions with a general focus on state crime laboratories. On the other hand, some states have commissions, which focus on specific issues on cold cases and the backlog of biological evidence cases (National Conference of State Legislatures, 2013).

Oversight roles are critical because research has established that there are systemic failures in the management of testing processes (Biben, 2011).

DNA requirements for convicted offenders

All states gather DNA samples from suspects and criminals engaged in specific crimes for the state and federal data banks. Most states collect DNA samples from felony offenders with the exception of Idaho. Some states have increased the number of criminal activities for DNA samples. For instance, California gathers DNA samples for all forms of felony and misdemeanor offenses.

DNA requirements for certain arrestees

Many states have focused on DNA samples from suspects and convicts of certain crimes. However, laws vary from state to state because arrestees may not be guilty of the offense. Some states have laws that allow officers to gather DNA samples from arrestees.

There are challenges of “privacy and the issue of Fourth Amendment rights” (National Conference of State Legislatures, 2013). Some states (Minnesota, Maryland, and Tennessee) have included judicial decisions on “a probable cause for an arrest in order to clarify such challenges” (National Conference of State Legislatures, 2013). In case there is probable cause for an arrest, then officers are free to put DNA samples into DNA databases.

Removal of DNA samples from the DNA database is also a source of concern for arrestees after the court declares that the suspect is innocent or in cases of dropped charges. Some states (South Carolina, Vermont, and Texas) may “automatically remove DNA samples from their databases while others (Alabama, Arizona, and Arkansas) require such people to file for a petition in order to have their samples removed” (National Conference of State Legislatures, 2013).

Post-conviction DNA testing

Some 48 states have laws on post-conviction DNA testing. “Only Oklahoma and Massachusetts do not have such laws” (National Conference of State Legislatures, 2013). Convicts who believe that they are innocent can get post-conviction DNA testing under the law (Justice Project, n.d). However, this may vary from state to state based on the classification of a crime. For instance, Hawaii and Idaho allow all convicts to “apply for post-conviction DNA testing, Alabama and Kentucky only allow convicts of capital crimes to seek for post-conviction DNA testing” (National Conference of State Legislatures, 2013).

Different states also have various approval criteria. For instance, applicants must show actual innocence or some degree of innocence.

Laws also account for the preservation of DNA samples. This is imperative because post-conviction would be meaningless without the original biological evidence from the crime scene. Post-conviction is an opportunity for courts to correct wrongful convictions.

Federal DNA funding opportunities: The Justice for All Act

The Justice for All Act provides funding opportunities for state and local forensic laboratories. There are four main areas under the criminal justice system and crime victims, which the Act favors. The aim of the Act is to protect crime victims, reduce huge backlogs of biological evidence from crime scenes and unresolved cases of convicted fellows. It also aims to enhance and expand the testing capabilities of federal and state forensic laboratories.

The Debbie Smith Act of 2004 focuses on improving the testing capacities of forensic laboratories by providing grants and funds for analyses of DNA samples. Laboratories should facilitate analyses of rape kits and biological samples from the crime scene of sexual assaults. They also analyze samples of unknown offenders.

The DNA Sexual Assault Justice Act of 2004 allows for grants to stakeholders involved in sexual assault cases. Such people can undergo training, acquire technical knowledge, education, equipment, and information necessary for identification, collection, storage, transportation, and analysis of biological samples.

The Innocence Protection Act of 2004 has Kirk Bloodsworth Post-Conviction DNA Testing Program for wrongfully convicted offenders. States get funds for such tests under this Act.

The Scott Campbell, Stephanie Roper, Wendy Preston, Louarna Gillis, and Nila Lynn Crime Victims’ Rights Act aims at providing grants for improving the rights of victims. It focuses on reasonable protection of the victim from the offender, provisions of information related to court proceedings, and the statuses of the accused. The Act ensures that victims get a full hearing, fair treatment, timely restitution, avoidance of delay, and consultation with the attorney.


This paper has explored key topics in the use of DNA samples in criminal cases. DNA samples have proved to be exceptional tools for solving criminal cases where evidence may be difficult to collect or locate the suspect. DNA samples confirm the identity of a known suspect or an unknown one. However, DNA testing may not be perfect due to contamination of evidence during various stages of handling, transporting, and analyzing samples. These topics provide basic information about the forensic criminal investigation.

There are other topics of interest in DNA testing in criminal law. Such topics look at various issues like analysis processes, sample processing, and various types of evidence analysis. Others include collecting evidence, crime scene integrity, transportation, and chain-of-custody.


Biben, E. (2011). Inspector General Biben Finds Systemic Failures in Nassau Crime Lab Procedures, Management and Oversight. Web.

James, N. (2012). DNA Testing in Criminal Justice: Background, Current Law, Grants, and Issues. Washington, D.C: Congressional Research Service.

James, R. (2009). A Brief History of DNA Testing. Web.

Justice Project. (n.d). Improving the Practice and Use of Forensic Science: A Policy Review. Washington, DC : The Justice Project.

National Conference of State Legislatures. (2013). DNA Laws Database Topic Summaries. Web.

National Criminal Justice Reference Service. (1999). What Every Law Enforcement Officer Should Know About DNA Evidence. Web.