DNA Evidence and Forensic Science in Solving Cold Cases

Introduction

Shortly after dawn on Tuesday, November 22, 1983, the body of a fifteen-year-old girl was found brutally raped and strangled on a narrow dirt footpath near the English village of Narborough in Leicestershire. Her name was Lynda Mann. A semen sample taken from her body was found to belong to a person with type A blood and an enzyme profile that matched only 10% of the adult male population. Even though a massive manhunt was launched, the case remained unsolved. Three years later the killer struck again, this time killing fifteen-year-old Dawn Ashforth in almost the identical spot where Lynda's body was found. Semen samples recovered from Dawn's body revealed her attacker had the same blood type as Lynda's murderer. Even though police knew the murders were committed by the same man, it took four years, a scientific breakthrough, and blood samples from more than four thousand men before the real killer was finally brought to justice (Lee, 1993).

Solving a murder is never easy. For the most part, unless law enforcement officials obtain a confession, it is often difficult to make an arrest and even harder to obtain a conviction without eyewitness testimony or compelling DNA evidence. Many television shows like Law & Order and CSI have glamorized the effectiveness and efficiency of the latest advances in forensic science, including the application of DNA matching to link murderers to their victims. Within the space of an hour, these fictional detectives solve murders that could take years to resolve, even with the best scientific minds working around the clock. On TV, the police always find DNA samples that are uncorrupted and rush them to a lab for near-instant processing. The bad guys always leave something behind: a partial thumbprint on a nightstand, skin under the victim's fingernails, even trilobal carpet fibers later matched to the trunk of the murderer's car.

In the real world of forensic science, things are not always so straightforward. DNA was not used to solve criminal cases until the 1980s. The first murderer to face justice based solely on DNA evidence found at a murder scene was Colin Pitchfork, who in 1988 was sentenced to life in prison for the murders of Lynda Mann and Dawn Ashforth.

This research paper explains what DNA is and how it is used to solve criminal cases. It discusses the implications of DNA fingerprinting in solving cold cases, with a focus on collection methods and applications in the state of California. This research analyzes the feasibility of DNA testing in solving cold cases and studies the impact that DNA fingerprinting has had on the forensic science community as a whole. The research is driven by studies and collection methods already implemented by the scientific community, as well as future methods of collecting and testing DNA evidence as they relate to the investigation of unsolved murders.

Defining DNA and the CODIS Database

DNA is generally used to solve crimes in one of two ways. In cases where a suspect is identified, a sample of that person's DNA can be compared to evidence from the crime scene. The results of this comparison may help establish whether the suspect committed the crime. In cases where a suspect has not yet been identified, biological evidence from the crime scene can be analyzed and compared to offender profiles in DNA databases to help identify the perpetrator. Crime scene evidence can also be linked to other crime scenes through the use of DNA databases.

In the late 1980s, the federal government laid the groundwork for a system of national, state, and local DNA databases for the storage and exchange of DNA profiles. This system, called the Combined DNA Index System (CODIS), maintains DNA profiles obtained under federal, state, and local systems in a set of databases available to law enforcement agencies across the country. CODIS can compare crime scene evidence to a database of DNA profiles obtained from convicted offenders. It can also link DNA evidence obtained from different crime scenes, thereby identifying serial criminals (Lee).

In order to take advantage of the investigative potential of CODIS, states in the late 1980s and early 1990s began passing laws requiring offenders convicted of certain offenses to provide DNA samples. When used to its full potential, DNA evidence may help solve — and may even prevent — some of the nation's most serious violent crimes. However, the current federal and state DNA collection and analysis system faces significant challenges:

• In many instances, public crime labs are overwhelmed by backlogs of unanalyzed DNA samples.
• Labs may be ill-equipped to handle the increasing influx of DNA samples and evidence. The problems of backlogs and outdated technology result in significant delays in the administration of justice.
• More research is needed to develop faster methods for analyzing DNA evidence.
• Professionals working in the criminal justice system need additional training and assistance to ensure the optimal use of DNA evidence to solve crimes and assist victims.

According to a recent article in Corrections Today magazine, "DNA evidence is one of the most powerful crime-fighting tools since the advent of latent fingerprint technologies. It has the ability to convict the guilty and free the innocent" (Wilson et al., 1999). DNA is an acronym for deoxyribonucleic acid, a double-helix molecule found in the nuclei of cells. DNA is the basic building block of life and is based on the arrangement of four chemicals. "The arrangement of the three billion pairs of bases in each DNA molecule is different for everyone (except identical twins). An individual's DNA is the same in every cell, from the moment of conception to death. A person's DNA in scraped skin cells will be the same as the DNA in his blood, saliva, organs, semen, or hair" (Wilson et al.).