Eureka moments of forensic science

AS we reach the end of 2010, we all look back and ask, “what have we achieved?” As such, it seems an appropriate time to look back at the uses to which we have put forensic science over the centuries.

The science has only really been standardised in the last century; prior to that, criminal investigation relied pretty much on confessions and witness testimony.

But throughout history there is evidence of the application of scientific principles to address certain issues.

One of the most famous historical examples is taught to primary school children. Archimedes was asked to determine whether or not a crown made for King Hiero II was pure gold. The king felt that the goldsmith who made the crown has stolen some of the gold and replaced it with the relatively cheaper silver.

If you had equally-sized blocks of gold and silver, the gold block would be heavier — gold is more dense. So a pure-gold crown would have a higher density than a crown with some silver in it.

To work out the density of the crown, Archimedes needed to know two things: its weight and volume.

The weight could be easily calculated with scales, but its volume was a different matter.

How could Archimedes work out the volume without melting down the crown?

We all know the rest of the story: musing on the problem in his bath, he realised the water level rose when he got in — and that the volume of water being displaced was the same as the volume of the object causing the displacement — namely his body. There followed, literally, the first “Eureka!” moment...

So he placed the crown into a vessel of water and measured the displacement. With the two figures he could work out the density of the crown and found it did contain silver.

One of the earliest recorded accounts in Britain was in the 18th century where someone was shot in the head by a highwayman. Upon examining the corpse a pellet and a piece of paper wadding — used in the pistol to hold the projectile and gunpowder firmly together — was recovered.

A suspect was found; who had a piece of paper in his pocket that had a corner torn off. The paper wadding matched the torn piece of paper perfectly and based on this, John Toms was convicted for murder. This is the earliest known example of a “physical fit”.

Even though the apparent uniqueness of fingerprints has been recognised for quite a long time, being used on clay tablet as a method of authentication, it was not until 1892, when Sir Francis Galton published a book about fingerprints and how they can be used in criminal investigations, that its forensic relevance was recognised.

That same year, Argentina saw the first conviction using fingerprint evidence: a bloodstained fingerprint matched that of a woman who was arrested for the murder of her children.

We jumpt forward again, to 1984, when the realisation that DNA profiling could be used in criminal investigations was made. Professor Sir Alec Jeffreys of the University of Leicester published his results in 1985 in the journal Nature, and in 1986 the first conviction involving DNA evidence was made.

This case - the murder of two girls by Colin Pitchfork – was also the first to use mass DNA screening.

The history of forensic science is littered with milestones, but they aren’t always recognisable as such. It is frequently said that Doubting Thomas from the Bible practiced principles of forensic science, by refusing to believe Jesus was dead until he laid hands on him.

St Thomas is even considered by some parties to be the Patron Saint of forensic scientists.

As we look forward to 2011 we can only wonder what milestones are yet to come.




::Graham Williams is senior lecturer in forensic science at the University of Huddersfield, and a consultant forensic biologist