Blog Guest Contributor: Marianne du Toit Pieterse 

‘Where there is no imagination, there is no horror’ (Sherlock Holmes)

The Crime & Investigation and Investigation Discovery channels on South Africa’s paid entertainment provider are presumably some of the most popular channels.  Whilst living in a violent society, we are fascinated with the gory details of a crime and the intricacy of the investigation that often lead to the arrest of the perpetrator.  If you’ve watched a few crime series’, you probably consider yourself an armchair sleuth trying to identify the guilty party before the investigators do.

Before the introduction of Deoxyribonucleic Acid – commonly known as DNA – in the mid-80’s, law enforcement relied solely on fingerprints, footprints, blood splatters, microscopes, credible eyewitnesses and good old-fashion police investigation in their quest to solve the crime.

Winds of change

DNA is now considered one of the most important discoveries of the 20th century and is considered the most accurate testing method available.  It was first used forensically in a cold murder case in 1986 of two teenagers who had been raped and killed in Leicestershire, UK in 1983 and 1986 respectively.  Not only has many cold cases subsequently been solved, but wrongly accused persons have also been exonerated.  The re-examining of evidence, in some cases 30+ years, is nothing short of astonishing.  Today, DNA analysis technology is far more advanced and can now be obtained from single cells.  Of course, collection techniques are vitally important too and DNA is considered one of the most important and effective tools in forensic analysis and crime fighting.

Using only DNA in any investigation would be futile without following proper protocols and procedures.  All evidence should be collected by investigating professionals as soon as possible, after the crime has been committed.  If not, crucial evidence will be lost due to crime scene contamination by (in some cases) the police themselves, the exposure to natural elements, the clean-up crew or when the scene is reopened to the public.

What does the evidence say?

The most important rule is that evidence must be relevant to the investigation.  These are categorised as follows:

  • Direct evidence is the strongest type and the evidence alone is the proof.  This could be the testimony of a witness who saw the incident first-hand.
  • Circumstantial evidence requires a deduction of facts from other facts (or fiction) and is not considered strong evidence.
  • Forensic evidence includes DNA, trace evidence, fingerprints or ballistic reports and can prove someone’s innocence or guilt.
  • Hearsay evidence is a statement made by a witness who is not present and is in most cases not considered as credible evidence.
  • Physical evidence, also termed real or material evidence is in the form of a tangible object – fingerprints, a firearm or tyre casts from a crime scene.

Into the mind of a perpetrator

Criminal profiling (also known as mind hunters) is a strategy used by law enforcement agencies to identify likely suspects and can be used to link cases that might have been committed by the same perpetrator.

In 1974 the FBI formed a unit called, Behavioural Science Unit (BSU) to study serial predators.  Profiling involves the investigation of a crime in the hopes of identifying the guilty party – or an unknown perpetrator – using crime scene analysis, forensic psychology and behavioural science.  The offender description usually includes psychological factors such as antisocial patterns as well as demographic variables which includes age, race and geographic location.

In the investigating phase of a criminal case, profiling is used to determine whether crimes could possibly be linked.  It is also used to predict the personality and lifestyle characteristics of an unknown subject.  It can even determine what information to be included in a search warrant and how he/she may react upon apprehension.

Real heroes don’t wear capes; they wear uniforms and badges.