Using DNA to solve crime

Vital questions relating to crime and punishment have been answered by the science of DNA (deoxyribonucleic acid). Wrongfully convicted rapists, murderers, even death-row inmates have been set free and the real culprits have been caught and convicted.

DNA evidence helped prove the innocence of three high-profile Canadians convicted of murder: David Milgaard, Guy Paul Morin, and Thomas Sophonow. James Driskell was also released based on DNA evidence. According to the Death Penalty Information Center in the United States, 75 people on death row have been exonerated because of DNA evidence since 1992.

DNA evidence can be patches of blood, semen or saliva, a tear drop, strands of hair, slices of skin. It can also be collected from just a few dozen cells, a sample much too small to be seen with the human eye.

According to Dean Hildebrand, a forensics DNA expert with the forensics department at the B.C. Institute of Technology, the science is all about connections. "Today's technology allows for very accurate associations to be made," he says. Hildebrand says the technology is very like fingerprinting in accuracy. Except a much smaller bit of evidence is required, and wearing gloves may not be enough to avoid leaving evidence.

Data banks have information on millions

Local DNA data banks are connected to national DNA data banks, which could be connected to international databanks with information on millions of felons.

The RCMP have established a DNA Data Bank, which is available to all law enforcement agencies across Canada. This information will enable crime investigators to identify suspects, eliminate suspects, link crime scenes where there are no suspects, and determine if serial offenders are involved in a crime.

It cost the RCMP $10.6 million to establish the data bank, and last year cost $2.5 million to operate. The RCMP expect that cost to rise to $5 million, once the data bank is operating at its full capacity.

Depending on the offence, a convicted criminal can be compelled to provide a sample for the bank. For certain offences, including murder, manslaughter and sexual assault, offenders are required to provide a sample. For others, including impaired driving, assault and robbery, it is up to a judge's discretion to order a sample be taken. As of March 2005, over 75,000 samples had been entered into the database. Nearly 3,000 matches had been recorded between samples and evidence.

According to the DNA Data Bank's annual report, the technology isn't used just for major murder cases. Most of them involved break and enter or robbery cases.

Delays can be dangerous

Early in 2001, the RCMP decided to use a private firm to analyze DNA samples from crime scenes, ranging from burglaries to homicides. The move was prompted by criticism of undue delays of DNA analysis by police forces, which former auditor general Denis Desautels warned could endanger public safety because criminals have more opportunity to re-offend.

A classic instance of such a delay was a DNA sample belonging to sex-killer Paul Bernardo, which was stored in a lab for months until it was analyzed. The DNA sample had been collected at rape scenes in Scarborough, evidence in the hunt for the so-called "Scarborough rapist," which turned out to be Bernardo. While the DNA samples languished in the lab, Bernardo kidnapped and murdered Leslie Mahaffy and Kristen French.

DNA testing used to be a slow, expensive process, taking months and costing tens of thousands of dollars. Now the testing can be done quickly, in a matter of days, for as little as $250. But Dean Hildebrand says procedures that need to be followed, combined with heavy caseloads, mean results can easily take weeks.

DNA can also be used in so-called "cold" cases, those that have remained unsolved for years. Investigators can use new techniques on old evidence. Recently, police in Ontario exhumed the body of Lynn Harper, who was sexually assaulted and strangled in 1959.

Hildebrand says finding some sort of evidence that would point to a suspect after all those years is "a long shot at best." That's because most of the types of DNA left by a murder or sexual assault would have degenerated already.

Hildebrand does say that some evidence can remain intact for years. Even bodies that have been buried would yield useable hair and bone samples decades, or even thousands of years later. It could be used to identify someone, or determine their lineage.

But DNA evidence is not always the magic bullet. "It is only as powerful as it is relevant in a given scenario," according to Chris Asplen, executive director on the National Commission on the Future of DNA Evidence.

What he means is that there may be no DNA sample found at a murder scene, but other evidence still can lead to legitimate convictions. Samples can also be contaminated. And there is always the danger that DNA samples, as with any other evidence, could be nefariously "planted" at crime scenes to link an innocent person to the crime.

What DNA evidence has done is focus attention on shoddy police work and court procedures. It has also drawn attention to the efficacy of capital punishment because once a person has been executed, DNA tests may posthumously restore reputations, but not lives.

Non-criminal uses for DNA tests:

• Identification of anonymous corpses (John and Jane Does). Samples can be gathered from skeletal remains of missing persons (bones, hair) and compared with samples from family members of the missing person.
• The military is increasingly using DNA profiles in place of traditional means of identification such as dog tags. New recruits now routinely supply blood or saliva samples, which are stored and used to identify soldiers killed in action.
• Medical scientists use DNA testing to determine the likelihood of family members inheriting such ailments as Alzheimer's disease.
• Anthropological scientists also do DNA testing to study human evolution by examining ancient skeletal remains, and human migration patterns by examining living people around the world to determine where different races originated and diversified.
• In 1998, the journal Nature documented DNA tests done to determine a paternity case that involved Thomas Jefferson, the third president of the United States. The hypothesis was that Jefferson had fathered children by one of his slaves. DNA tests determined indeed he did.