Criminals take. Our hard-earned belongings, our peace of mind, our lives. But they also leave a damning trace of themselves behind: their most personal signature, the unique DNA every human being sheds in skin cells, hair follicles and body fluids.
The crime may also leave its mark on the criminals themselves, or on their own environment away from the crime scene.
Blood from two of the victims was identified on a pistol and clothing found at one of the suspects' homes, thus putting them at scene of the crime.
In another case of successful conviction achieved through DNA forensics, the killer's spittle was found on a cigarette stub left at the scene of a murder at a Cullinan dairy farm three years previously.
There is no question that DNA evidence can be of vital importance in solving criminal cases such as this. But the efficient police work in the Lindley case is not typical of the generally unsatisfactory state of DNA forensics in South Africa.
Critics such as those driving the DNA Project, an organisation pushing for the expanded use of DNA evidence and the National DNA database, say that DNA collection, processing and analysis is beset by problems that include inadequate DNA profiling equipment and laboratories, outdated information systems, overwhelming caseloads and backlogs, and lack of training.
Learning to protect DNA evidence
One area where we can improve our DNA forensics is in the quantity and quality of evidence collection.
Crime scene DNA is fragile, and easily lost or contaminated. Evidence is frequently destroyed simply because those first on the scene, whether members of the public, security personnel, emergency services or even police officers, are not aware of basic procedures for containing the crime scene and protecting evidence.
The DNA Project recommends the following steps members of the public can take to help protect evidence:
If you were witness to the crime, or are first on the crime scene:
- As far as possible, avoid direct contact with the scene yourself, and keep others from entering.
- Tell the investigating officer (IO) what happened in as great detail as possible: where the attacker came in contact with the environment i.e. where he walked, what he touched, and if there was a particularly “high contact” area. The IO can focus on such areas for sampling.
- Ask yourself: Did the criminal smoke, eat or drink? If so, where is the cigarette butt now? Did he use a glass or spoon, or leave half-eaten food? Did he ejaculate or spit on any surface? Did he wipe himself; where is the towel or toilet paper he used? Such information can greatly assist the IO with finding valuable evidence.
All information you provide must be thoroughly documented in a sworn statement to be used as part of the evidence when the case is prosecuted. Physical evidence collected by the IO will help prove your account of events and link the suspect to the crime.
In cases where a person has been physically attacked, the victim's body may also be a source of DNA evidence.
If you have been assaulted, preserve evidence by not bathing or removing your clothing. If you have been raped, do not eat, drink, brush your teeth or hair, or urinate until you have been medically examined and samples taken for DNA. If you must urinate, do so into a container which you then keep closed.
Read more on what to do if you have been raped.
Expanding the National DNA Database
At present South Africa's National DNA Database (also referred to as the Forensic DNA Database) contains about 120 000 DNA profiles, which is very small: the United States' and United Kingdom's databases each contain over 5 million profiles.
One reason our Database is so limited is that it currently consists only of DNA profiles derived from samples collected at crime scenes, and from persons arrested as suspects.
Other countries' National DNA Databases include the DNA profiles of convicted offenders, but ours does not. Vanessa Lynch, founder and executive director of the DNA Project, explains that SA's lack of a Convicted Offender Database is a result of outdated legislation.
South Africa does not have specific legislation that regulates the existing DNA Database. Currently, section 37 of the Criminal Procedure Act, 51 of 1977 is the only legislation that deals with biological means, such as fingerprinting and blood samples, used to link suspects to crimes. As it was drafted over 30 years ago, before the advent of DNA profiling, there is unsurprisingly no mention of DNA evidence collection.
Says Lynch: "An amendment to the Criminal Procedures Act would allow for the database to be expanded to include DNA profiles of offenders. Currently in SA you can't take a profile from a convicted offender. But with the high rate of re-offending, this information on a database could be very useful.
"Generally, people who commit one crime commit other crimes in future. If DNA evidence collected from a crime scene could be run through the Database and perhaps come up with a match, this may provide investigators with a lead in cases where there was none before."
The change in legislation the DNA Project hopes for, namely the Criminal Law (Forensic Procedures) Amendment Bill (the "DNA Bill"), calls for all DNA profiles of convicted criminals to be included in the Database, regardless of when the person was convicted.The DNA Bill was approved by Cabinet in April 2013 and formally introduced into Parliament on the 8 May 2013. If passed, the DNA Project reckons it will have "a profound impact" on our the criminal justice system.
In other parts of the world, effective National DNA Databases that include convicted offender profiles have been shown to act as a deterrent to criminals. They also act an inducement to confession: in Britain, for example, 85 percent of suspects plead guilty when presented with a match of their DNA to the crime.
Keeping a DNA profile of a convicted offender in a database is essentially a very similar concept to keeping his fingerprint on record, says Lynch.
Improved sampling methods
In South Africa, when samples are taken from people, usually suspects linked to a crime, the sample takes the form of a vial of blood, and must be drawn by a medical practitioner.
International practice permits taking these samples with a buccal swab - the earbud-type swab often seen in crime series like CSI, which is swiped inside the cheek to collect epithelial cells. DNA is then extracted from the cells in the lab.
The new forensic DNA Bill suggests that South Africa adopt the use of the buccal swab, because it is easier, quicker and less invasive than drawing blood, and could be performed by a police officer rather than a medical practitioner. It also avoids an arrestee from being held unnecessarily.
Lynch, V (2011). Darwin Lecture, May 2011. Africa Genome Education Institute, University of Cape TownNews24 (2011). 5 guilty of Lindley farm murder
News24 (2011). DNA evidence links Lindley suspects
The DNA Project (2011). Official website.