Poisons have been used since ancient times to kill. They are the cleanest and most efficient way to murder; cheap, easy to buy and simple to administer. It’s usually a careless slip-up which helps to convict the killer.

The web is a powerful tool that can be used to threaten and subjugate, and the anonymity it affords means it can be used by criminals, terrorists and even governments for social, ideological, religious or political ends.

Two of the trickiest things to accurately pinpoint are the time and cause of death. The person responsible is a pathologist. If there’s no obvious cause, then it’s time for tissue and fluids to be analysed in the minutest detail.

Crimes have been solved by establishing the author and authenticity of a document, but it isn’t easy. You not only have to be able to identify handwriting but also the age of the document, the ink type – even the computer on which it was written.

The image of Sherlock Holmes running around with a magnifying glass may seem quaint, but it’s one of the most useful pieces of scientific equipment available. Only nowadays, the magnifying glasses are more sophisticated.

The gun is perhaps man’s deadliest weapon, used for centuries to kill, maim and defend. Until the 1900s there was no method for tracing bullets back to the weapons that fired them. Discover how an American doctor triggered the science of ballistics.

Many murderers go to great lengths to destroy their victim’s identity. But getting rid of a human body is not at all easy. How do forensic scientists identify a victim when there are only tiny scraps left behind?

Forensics is most often used on physical clues at crime scenes, but there is another tool at investigators’ disposal, one which deals with the science of the mind. ‘Psych’ profiling is now widely used in the USA, the UK and beyond, but it is not an exact science.

Fingerprinting has been used as a foolproof method for over a century. Each of our fingerprints is unique, made up of tiny ridges and corrugations. It is this distinctiveness that makes prints so invaluable for fighting crime and a trump card for prosecutors in court.

Blood is the most difficult bodily fluid to remove from a crime scene. And with blood spatter analysis, even a speck can prove the difference between a killer walking free and an innocent man serving time.

Genetic profiling has been hailed as our most important advance in the forensic fight against crime. The pioneering work of Dr Alec Jeffreys has created a whole new discipline, and its full potential has still to be realised.

Teeth are ideal for identifying human remains after muscle, skin and organs have wasted away or been destroyed. Whether used in anger or defence, the marks they make are significant clues that can help investigators solve the most complex of crimes.

Killers love explosives and fire because they do two things at once; they obliterate the victim and any traces that the perpetrator might have left behind. At least, that’s what many of them think…