The prints themselves are made up of sweat and grease, including a complex mix of cholesterol, amino acids and proteins.
"The chemicals in these fingerprints can be analysed," said De Puit. "Some disappear over time and it's the relative proportions of these chemicals that allow us to date a fingerprint."
Previous attempts to crack the formula for dating fingerprints failed because they focused on the amounts of chemicals, rather than their relative proportions, De Puit said.
Taking into account the temperature of the original prints' surroundings, which affects the speed of deterioration, forensic experts can now date fingerprints to within "one or two days", up to 15 days.
The new technique needs to be extensively tested on real crimes scenes, leading to the creation of a database, before it can be used in prosecutions, hopefully "within a year", De Puit said.
As the database expands, so should the technique's reliability, allowing police to date fingerprints from several years before.
In the meantime, De Puit and his team are working on another revolutionary analysis technique: analysing fingerprint chemicals to determine a suspect's drug or food consumption.