Forensic scientists have successfully recovered fingerprints from food in a breakthrough which could lead to even more evidence being gathered in future police investigations.
The scientists at Abertay University in Dundee modified an existing technique to get fingerprints from fruit and vegetables - said to be the first time this has been achieved in the UK.
In the past, foods have proved difficult surfaces to recover prints from, so are often overlooked as items of evidence.
The scientists have published their research in a forensic science journal Science & Justice, meaning that others will now be able to replicate their results.
Dennis Gentles, a former crime scene examiner and forensic scientist who has worked at Abertay University for the past 10 years, said: "Although there are proven techniques to recover fingerprints from many different surfaces these days, there are some surfaces that remain elusive, such as feathers, human skin, and animal skin.
"Foods such as fruits and vegetables used to be in that category, because their surfaces vary so much - not just in their colour and texture, but in their porosity as well.
"These factors made recovering fingerprints problematic because some techniques, for example, work on porous surfaces while others only work on non-porous surfaces."
He added: "It may not seem like much, but a piece of fruit might just be the only surface that has been handled in a crime scene, so developing a trusted and tested technique to recover fingerprints from such surfaces is something to be valued by crime scene examiners."
The fingerprints were recovered using a method initially designed to take prints from the sticky side of adhesive tape.
The scientists found that powder suspension (PS) - a thick, tar-like substance - produced a clear, high-quality mark on smooth-surfaced food items such as onions, apples and tomatoes.
Mr Gentles said: "Although powder suspension was initially developed to recover prints from the sticky side of adhesive tape, it's since been found to work on other surfaces, so we wondered whether it would work on foods, as this was something it hadn't been tested on before.
"The smooth surface of an apple is very different from that of sticky tape, though, so such a thick substance wasn't going to produce the same results on such a different surface.
"So, we tried altering the formulation a bit, making it more dilute than that suggested by the Home Office, and found that it out-performed all the other methods we tested.
"Although there's still a considerable amount of research to do before we can recommend techniques for all types of foods, we've shown for the first time that it really is possible to recover fingerprints from them - something that was previously thought to be unachievable.
"This means the police will now be able to gather even more evidence to present in court, adding more weight to their investigations."