Forensic Science

by Read Listen Learn

Catching criminals used to be an art but, as medicine and technology have improved, it has become a science called forensics. It has also become very popular on TV and most police programmes now include a strong 'forensics lab' story in the show. There are also a lot of forensics-based documentaries. Unsurprisingly, the demand to study and work in this field among youngsters has gone through the roof. These days, forensic science is so complex that people who want to work in it need to specialise early on.

And the choices of specialisation are vast. You could go into forensic entomology, for example, which is the study of insects in relation to dead bodies. In practical terms, the specialist can tell how long the body has been dead by judging the age of the flies and other insects now eating the corpse. Not very nice, but it does help to put murderers in prison.

Another example is forensic psychology in which expert psychologists decide what type of person has committed the crime or crimes. They may decide, for example, that the suspect they need is male, about forty, lives alone and works with computers, and had a very religious upbringing. Mostly, they get it about right and this helps the police to look in certain areas or investigate certain suspects a little more closely.

Then there are teeth and dental records: forensic odontology. What about identifying some grass or leaves found on the body but not around it? That's called forensic botany. Car paint from a hit-and-run? That would be forensic chemistry. Looking through a gangster's bank and financial details? That's forensic accountancy.

However, the ones we know best and that often get the best results in a trial are ballistics (guns and bullets), fingerprints, blood and of course DNA. We'll take a look at some of these but, first, where did it all begin?

The word 'forensic' comes from the Latin word 'forum' which meant a lot of things, including 'law court' so the word forensic means anything to do with a criminal case but, more recently, it has come to mean the physical evidence in a case and its presentation to the court.

The concept may have started with the Romans but they had almost none of the science and technology of today. They could tell if someone had been stabbed but not much more. Poisonings were often unnoticed which is why so many powerful men had 'tasters' to try their food for them. Really, forensic science, until about the 18th century was a question of trying to make guesses based on what you could see with the naked eye – not very reliable – so mostly, they used statements from witnesses, victims and the accused. It was largely an emotional process in which people were believed according to their sex, race or power; or their verbal skills.

As modern science started to advance rapidly, through the 18th and 19th centuries, so forensic science became possible. The first example was the autopsy, or post mortem, used to find out how someone had died. Obviously, if you know the cause of death, it is far easier to decide if the person was murdered and, if they were, the way they were murdered may help to identify a suspect.

Other developments came quickly, most usefully, fingerprint identification. It seems we all have different patterns and lines on our finger pads and so we can be sure that a certain person held, for example, the murder weapon.

Fingerprinting and other scientific methods of crime detection became very well-known through the fictional detective stories of Sherlock Holmes by Sir Arthur Conan Doyle, who, when not writing detective stories, was a medical doctor who knew all about the developments that were going on in forensic science. This meant that he could include 'state of the art' forensics in his detective stories – though it does all seem very primitive compared to today's sophisticated forensic labs.

Not all branches of forensics need science labs. Forensic linguistics is the study of language, written or spoken, to help solve a crime. A well-trained forensic linguist can often say just where someone grew up or what social class they come from just by listening to a recording of their voice.

When someone sent a voice recording claiming to be a dangerous killer, a forensic expert was able to say that the man speaking came from a small city in the north of England called Durham. That would have been impressive in itself but the linguist was able to connect the man to just a small neighbourhood of the city, a few streets with a couple of thousand people living in them. The man who sent the recording was eventually caught. He was a hoaxer (the real murderer had been caught years before) and he did come from exactly where the linguist said he had.

In written form, language has no accent but linguists can still tell a lot about the person who has written the letter. It doesn't matter if it's hand-written or typed because they are not looking at hand-writing (that's somebody else's job) they are looking for clues in the language. For example, in the little Lindbergh kidnapping over eighty years ago, some letters and notes were written by one of the kidnappers to arrange the ransom. It would later come out that the criminal was a German immigrant with poor English and, from the mistakes he made, the police were able to say that he was a German speaker, and with some education in his own language.

And there are many other fields and areas of forensics but too many to list here. However, we must mention DNA. This enormous scientific development of the last twenty years means that, even from microscopic and old pieces of physical evidence, we can get a unique genetic profile of a victim or criminal. The least little piece of hair, tiny amounts of sweat left on objects by the fingers or hands, or the traces left by someone sneezing on a window: all of these will give a DNA profile of the person. From that profile, we can get other information about the person like sex, ethnic background or medical problems, helping to narrow the field in any search.

What used to depend on blood and fingerprints is now based on DNA. It's not that blood and fingerprints are no longer used in criminal investigation – they definitely still have a very important role to play. It's just that DNA is so much more reliable and possible to get traces of.

However, we still do not have a 100% certain forensic branch. Even DNA can fail us in some circumstances. Closely related people, especially twins, can have dangerously similar DNA. Sometimes the DNA evidence presented in court will be from an incomplete sample or one mixed up with other DNA. The prosecution will claim 99.999% certainty or, put another way, only a one in a million chance that they are wrong and it is another person.

That sounds pretty good, right? Beyond a reasonable doubt. Until you consider that in a city like Tokyo or Sao Paolo, with populations of twenty-five million, this means that there are around twenty-five other people living within easy reach of the scene of the crime who may have been the actual criminal. Until the police find them and rule them out, it would not be fair to send the defendant to prison.

Also, criminals have used DNA to confuse police. In a small but growing number of cases, the criminal has thrown down DNA debris from other people not connected to the crime.

What does this mean in practice? One killer left the body of his victim, a female prostitute, on waste ground and left a used paper cup and some cigarette ends near her. He had taken these things earlier in the day from a restaurant table that somebody had just left. The police assumed that the DNA on the debris they found must belong to someone connected to the murder. This sent the search for the killer off in all the wrong direction and, in the time lost, the killer murdered two more victims and threw down a little more of his decoy evidence.

So, DNA is not a miracle solution to all criminal problems. Nonetheless, it is pretty good and it is helping to send real criminals to prison and keeping innocent people out. The other branches of forensics, just a few of them are mentioned above, are also becoming more reliable and helping to combat crime.

This has raised a civil liberties issue: should everybody's DNA be on file and available to the police? That way, many more criminals, especially murderers and rapists would be caught and caught quickly. On the other hand, should the police and government be allowed so much information about everyone, much of it information that could be abused in a number of ways?

The debate is still going on...