Police in St Helens are warning criminals their cards are marked.
The message came at the launch of a scheme to roll-out a forensic marking kit to deter crooks from domestic and retail crime.
A key part of the initiative is a forensic spray to be used in convenience stores against shoplifters.
The spray can be used by staff members to leave a mark on offenders and is only visible under ultra-violet light.
Chief Insp Jenny Sims said: “As well as offering homeowners extra measures against burglary, we are continuing our efforts to tackle retail crime.
”The force works closely with bookmakers, off-licenses and convenience stores and we offer crime prevention advice and point them in the direction of the most appropriate security measures. This has included fogging devices and electronic trackers.
“Retailers are now also using forensic sprays.”