Fingerprints Past and Present

In Who Killed Sir Harry by Eric Minns and Identical by Scott Turow fingerprints played an important role in each book.

In Who Killed Sir Harry the existence of a fingerprint from the accused, Alfred de Marigny, on a screen in the bedroom of the murdered Sir Harry Oakes was powerful evidence introduced by the Crown Prosecutor.

By the time the defence, led by barrister Godfrey Higgs, had finished challenging the fingerprint the prosecution case was in tatters.

The Duke of Windsor had called in a pair of Miami detectives for supposed investigative expertise. Captain James Barker was trained in the taking of fingerprints and their analysis. Yet he left his fingerprint camera behind when he rushed to the Bahamas.

Of the pair of fingerprints of the accused he said he found in the room one he claimed was on a panel of a wooden screen damaged by fire after the murder.

Immediate suspicion of his credibility arose because he never took photos of the fingerprint on the screen before lifting it off the screen. His actions meant there could be no confirmation of its location.

His evidence fell completely apart when it was shown that the fingerprint could not have come from the screen as set out by Cathleen LeGrand in her fine article “Another Look at a Bahamian Mystery: The Murder of Sir Harry Oakes: A Critical Literature Review” in the International Journal of Bahamian Studies:

Even more suspicious, the lifted fingerprint lacked any of the background detail  from the screen, detail that would normally be picked up. When asked to demonstrate in the courtroom, Barker could not replicate a clean lift of the print without the background detail. Higgs' conclusion—the detectives lifted deMarigny's fingerprint from some other object and not from the crucial screen..

The frame-up of de Marigny was established when it was shown Barker had manipulated the accused into drinking a glass of water. It was clear the fingerprint had come from the water glass rather than the screen.

In Identical the story takes place 65 years after the de Marigny trial. In Turow’s book the fingerprint analyst deals with the fingerprints of identical twins. They will be close to the same but not identical.

While they have same DNA (as science evolves it may be possible to distinguish their DNA) they do not have identical fingerprints. The book sets out how fingerprints are formed in the womb and can be altered by the hand of the foetus touching the wall of the womb.

If you prefer scientific language you can review "Mechanical Control of Tissue Morphogenesis" by Parth Patwari and Richard T. Lee in Circulation Research which sums up the process of forming fingerprints for a foetus:

However, the ridges are not always regularly spaced: there are ridges that divide and ridges that suddenly end. These irregularities are easily changed by small variations in their local environment, so they are not predetermined. Even monozygotic twins will have different positions in the uterus and experience a slightly different environment. In genetically identical twins, then, subtle differences in the mechanical environment of the embryo in utero are sufficient to drive a developing system toward different morphogenic outcomes.

As I looked for information on fingerprints of identical twins I learned that it has been difficult to locate fingerprints from children because they do not have sebum, the oily substance coming from the sebaceous glands. Adults with dry skin, for the same reason, have fingerprints that can be hard to find with traditional fingerprinting technology.

New technology, called micro-X-ray fluorescence, detecting such salts as sodium chloride and potassium chloride, can detect fingerprints left by dry skin fingers.

Most modern forensic crime stories, whether in books or T.V. series or movies, look to flashier forms of science than the search for fingerprints and their analysis. Yet the lowly fingerprint remains at the heart of forensic investigation.