A breakthrough in the way fingerprints are taken could lead to hundreds of cold cases being reopened.
The new method, to be revealed by Northamptonshire Police, enables scientists to visualise fingerprints even after the print has been removed.
An electric charge is applied to metal objects which have been coated in a fine conducting powder.
A removed fingerprint would leave a slight corrosion on the metal which would be revealed by the powder.
Northamptonshire Police's scientific support unit will reveal its discovery in detail in the Journal of Forensic Science, later this week.
The technique is said to work even if heat vaporises normal clues.
Dr John Bond developed the technique with forensic researchers at the University of Leicester.
"It's certainly possible hundreds of cold cases could be reopened because with this method the only way to avoid a fingerprint being detected is through abrasive cleaning as that takes a layer off the metal," Dr Bond said.
"It could work for gun crimes where bullets have been recovered and the offender may have left a fingerprint on the casing that has not been picked up by conventional techniques."