The invention and development of forensic techniques has proved essential when it comes to solving crimes, as this fascinating series reveals. The use of DNA profiling, ballistics and fingerprinting has led to the capture of some of the most notorious murderers and rapists in history, thanks to the tiniest, almost untraceable pieces of evidence left behind at the scene of the crime.

Crime Scene Investigation
The first thing that forensic experts do when there's been a murder is of course, examine the scene of the crime itself. This is a very painstaking process but one that is so fascinating and rewarding that there's even been a action-packed US TV series named after it!

Basically, every inch of the crime scene is recorded for later study, including the more obvious such as how the victim died, as well as the more subtle indicators, like the state and situation of the body or any foot or tire track impressions left by the killer fleeing the scene.

Any physical evidence is collected for subsequent analysis. The body is removed, as is any potential murder weapon, clothing or documentation that might hold a clue to the identity of the killer or at least establish motive. After all this has been done, forensic experts also look for trace evidence, such as fingerprints, blood and DNA samples.

What is DNA?
DNA stands for Deoxyribonucleic Acid and is the chemical found in virtually every cell in the body and which carries genetic information from one generation to the next. When translated, this information determines our physical characteristics and directs all the chemical processes in the body.

Except for identical twins, each person's DNA is unique, with half inherited from our father and the other half from our mother. By taking DNA samples from any body cells, including blood, semen, saliva or hair, forensic detectives can analyse and measure the strand of any DNA found at a crime scene, making this unique biological pattern instrumental in confirming a killer's identity. Unless twins did it, but then it's fifty-fifty!

Fingerprint Evidence
While a lot of emphasis is placed on the use of DNA profiling, forensic experts never forget that the majority of murderers are caught on the strength of fingerprinting evidence.

Fingerprints are one of the best forms of physical evidence. You don't need a Ph.D. to understand that your own fingers contain a map of ridges and whirls that is completely unique. Fingerprint evidence rests on two basic principles:
A person's "friction ridge patterns" - the swirled skin on their fingertips - never change and no two people have the same pattern of friction ridges.

In many countries there now exist nationwide databases available for rapid computerised searching and comparison. This makes it very easy for forensic experts to match those left at the scene of the crime with any known offenders, and so either eliminating or including them in their search for the killer.

Ballistics
If someone has been shot, the science of ballistics is often a highly important element in finding out who dunnit. Taken from the Greek word 'ba'llein', meaning 'throw', ballistics deals with the motion, behavior and effects of bullets.

There are many elements that ballistic specialists take into account, including the pressure of gases in a gun, direction of impact in the body, gravity, temperature, or air particles - all of which can create a profile of what kind of gun was used, from where they shot the victim and how close they were when they did it.

When studying the assassination of US president John F Kennedy in 1963, ballistics famously dismissed the initial claim by police that there was a single gunman shooting from behind. Ballistic science suggested that there were in fact several gunmen firing from different locations. This popular theory is still controversial as it implies an elaborate conspiracy and the debate rages to this day.

Find out more
More often than not there is no single element from a murder that can catch a killer; the crime is often solved from a combination of all of the above elements, combined with psychological profiling of the killer, the detailed autopsy of the body once it's removed, eyewitness accounts and so on.

However, Forensic science is vital in uncovering clues that cannot lie. In incriminating piece of evidence left at the murder scene by the killer in a panic, no matter how small, can lead to their ultimate undoing!