A hand washes up on a beach …

You’d be wrong in assuming that a hand on its own would have little to offer forensic investigators trying to match it to a body. Let’s imagine a single hand found on a beach by an early morning swimmer: What can investigators learn from it that will help them uncover the backstory?

“Hands can tell a lot about a person and with their role in our daily lives, and are highly connected to who we are; they tell the story of our lives,” Dr Cam Mackay says.

Fingerprints may not be helpful (Image: Wikimedia Commons/coolcaesar)

Dr Mackay, who was a Queensland Police Forensic officer before becoming a hand surgeon, says hands can reveal a lot of information to investigators.

Fingerprints are helpful, but only if the person belonging to the hand has a record of those prints on file.  And in this instance – with a hand washing up on a beach – there’s a chance fingerprints may already be compromised after being immersed in the sea.

Think about your fingers after you’ve been swimming or lying in a bathtub for a while. They get ‘pruney’ and wrinkled and that’s essentially the problem in a forensic context.

“In summer, in Australia, with an exposed body, fingerprints can be well into advanced decomposition within days so that’s when police would go straight to dental records,” Dr Mackay says, adding that the skin can “peel off like a glove”.

“There are actually stories where the skin has sloughed off the hand and the examiner has essentially put it back on like a glove and printed the fingers.”

So, in the absence of fingerprints – and dental records in this case – what other options are available to police in their quest to solve the mystery?

Hands can reveal a lot (Image: Pexels/Italo Melo)

Biometrics, the technical term for body measurement, can give some clues as to the gender or age of the person. Forensic anthropology, the study of bones, will also reveal information about age or previous injuries.

“You’ve got 27 bones in the hand, and each one has a story,” Dr Mackay says.

“We use our hands all the time, we’re much more connected with them, so they’re more likely to be injured, or show signs of ageing. If we’ve just got a bit of anatomy like a thigh with a femur in it, we don’t have much at all but in a hand, we get to analyse the joints, we can see the arthritis, we can match the arthritis, and we can see evidence of previous surgeries or injuries.”

Four tiny holes drilled into a finger bone would tell us the person had previously broken that finger, had a plate and screws inserted, and then had them removed. If the hardware was still in place, investigators could review the brand and use that information to pinpoint where the surgery took place and when, as they did for a mysterious man found on a moor in northern England in 2015.

In some instances, the bones could even shed light on the way a person died. If a hand was put up in self-defence and was struck by a sharp object, there may be lacerated tendons or cuts deep through the volar structures, leaving markings on the bones.

Arthritic changes could reveal the age and gender of the person and perhaps even what kind of work they might have done or hobbies they may have had, like manual labour or enthusiastic knitting. Because arthritic changes in the base of the thumb are more likely found in women over 40, signs of that could immediately narrow the focus for investigators.

Another less invasive method would be in the appearance of the hand, which can help investigators build a profile of the person. Scars, tattoo and jewellery can be identified by family and friends while, with the help of forensic chemistry, nail polish can be scraped off and analysed to give some idea of the brand and where it may have been purchased.

Hints from hands can provide significant information (Image: Pexels/Kat Wilcox)

So here, in our imaginary case study, we have fingerprints (but no criminal record to cross-match), a healed finger fracture fixated with screws now removed (possibly traceable with hospital records), some mild basal thumb arthritis, signs of a defence wound, a gold ring showing wear, worn on a finger with a small callus (it’s never taken off), and pearl pink nail polish of a colour no longer commercially available.

All these facts once compiled by investigating officers, present a picture of the potential victim of – what appears to be – a crime. Thankfully however, these hints provided by the hand have greatly increased the police’s chance of solving the mystery.

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