Just how reliable is forensic science? Alan Coughlan weighs up the pros and cons of this phenomenon
Eyewitnesses have always been called on to identify criminals. Their accounts are invaluable to police investigations and lawyer’s cases respectively. They can visually tie a suspect to a crime scene and this adds weight to an argument against the accused. What, though, of the victim themselves?
In the mid-nineteenth century, a strange practice borne from so called ‘optography’ was used to try and identify criminals. The thinking was that the human eye functioned like a photographic plate, continuously absorbing and reabsorbing images and physically manifesting them at the back of the eyeball. Early forensic scientists would take close-up photos of murder victims eyes and try to view the last image that fell upon it. This was not a mere fringe practice and was indeed carried out on one Annie Chapman’s eyes by Scotland Yard. She was the second victim of Jack the Ripper.
One can easily guffaw at this practice today, but it was once thought to hold more water as a scientific theory than dactyloscopy known today as fingerprinting.
The road from what was once considered a very shaky and unscientific practice to a field which now helps convict criminals was long and complex. Along the way, certain methods have been invented and some were dropped due to elements of doubt in just how certain they can be.
“Indeed, many lawyers in America have recently complained of the “CSI effect” in which juries will take any forensic scientist’s word as gospel within the courtroom”
In what one might describe as recent history, upon discovering a murder, people would rearrange the body perhaps to presereve dignity, or a sense of decorum, and even clean up blood and other evidence. This seems impossibly stupid to us today, but there was a time when forensics were not really regarded as science at all. Postmortems were completely illegal in the UK initially.
Forensic science is incredibly familiar and at least in passing to the layman, owing to TV shows such as CSI, but its veracity both throughout the ages and today is hotly debated. Indeed, many lawyers in America have recently complained of the “CSI effect” in which juries will take any forensic scientist’s word as gospel within the courtroom. The problem with this is that forensic science is no different than any other field of science, as theories are constantly being tested, revised and reformulated.
Comparative bullet lead analysis is just one outdated form which was used for decades to identify bullets, by examining the chemical make-up of individual bullets and linking them to certain batches and sometimes even individual boxes. It was first used during the investigation into the assassination of John F. Kennedy, but was abandoned as a practice in 2005 by the FBI.
Dental records were used in the conviction of Jeffrey Dahmer – one of the most gruesome serial killers to ever live. A forensic anthropologist was called in to reassemble bone fragments to determine the identity of one of the corpses. A smashed vertebrae was identified from an x-ray of the victim when they were just thirteen-years-old. This showed up in dental records. Surprisingly, dental evidence is one of the areas being questioned in terms of its veracity in the courtroom in how effectively it can single out just one person.
Doug Lyle is a doctor who gives conferences to mystery novelists on how someone could successfully get away with murder. He says that when he goes to dinner parties, people will ask about their gall bladder or their prostate trouble, but whenever he meets a writer, they want to know how to kill someone. These kind of discussions bring up an interesting question. Is forensic science accurate and water-tight enough to prevent someone getting away with murder?
A period of five-and-a-half hours is roughly what a pathologist can pin down to a victim’s time of death to up to twenty-four hours after their passing. This is based on their body temperature. After the twenty-four hours, this five-hour period stretches until after only a few days, the time of death can no longer be determined.
This can cause huge problems in placing a suspect at a murder scene if the time of the death is not known. Bizarrely, it is in the study of insects which inhabit the body almost straight after death that the death can accurately be ascertained even months later.
One forensic scientist has even pointed out that planting maggots at different stages of development on a freshly-killed corpse could confuse forensic entomologists. While not enough to completely stump scientists, it would buy the murderer time to get away. It seems that the key to a killer getting away with murder is in purposefully confusing those investigating.
In November 2006, Alexander Litvinenko fell ill in London with what was first thought to be gastroenteritis, which is a form of food-poisoning. However, quite quickly his condition worsened to include liver and heart failure, along with hair loss and then his death.
Radiation had been suspected at one point, but no tests detected any. It was only later when the cause of his poisoning was discovered that this made sense. He had been poisoned with polonium-210, a substance no one on record had ever been poisoned with.
Thus, no one could have known what was going on as events unfolded. The confusion which this caused not only stumped the doctors, but then the subsequent murder investigators. This gave the assassin ample time to flee, as foul play was not initially suspected.
The reason the polonium was not detected was because it emits alpha particles, not gamma radiation. Alpha particles will not pass through the skin and were not picked up by any equipment. This murder case was a clear example of sophisticated premeditation in this murder. Whoever was guilty knew just how to confuse the experts.
It has even been pointed out, with a touch of irony, that koala bears’ fingerprints are indistinguishable from those of humans. This, however, should not do much to dent the reputation of fingerprinting as a discipline in the courtroom.
Deception, of course, takes place in cases of murder nowhere near as sophisticated in their execution as the Litvinenko case. Murderers will destroy bodies, or hide them along with concealing murder weapons, and will even attempt to clean murder scenes to erase any evidence that could link them to the case. It is in these areas that highly specialised forensic scientists can catch out even the most cunning of killers. Single fibers of fabrics, fingerprints, DNA and even shoe prints can be used to convict suspects.
TV shows such as CSI and Forensic Detectives have familiarised the public with DNA profiling and blood-detecting chemicals like the eerie blue glow of luminol in the presence of blood. The chemical works by reacting with the iron in haemoglobin.
Luminol can have limited use in investigations, however, as it can become activated not just by blood, but by copper or even copper containing alloys which are present in bleach and which could be used to clean a crime scene.
What these limitations highlight is that a forensic investigation calls on a whole range of disciplines to convict a suspect, as sometimes individual tests can be picked apart in the courtroom. It is thus only in the building of a large and strong body of forensic evidence that a case can be won and a murderer convicted.