AN invisible dye can help catch armed robbers who target security vans.

Security companies now use an invisible marker dye that sticks to the robbers’ skin and clothes – along with the stolen cash.

The dye will link robbers to specific cash boxes.

There is also usually a highly visible dye in cash boxes which stain the offender and the cash, making the money worthless.

The new unique marker dye will provide vital evidence in court, linking the offender directly to the crime scene.

West Yorkshire Police has been working closely with cash courier G4S to introduce the specialist system that will spray the robbers and the stolen cash with liquid that contains a unique code specific to each individual cash box.

Although invisible to the naked eye, the indelible substance can be detected under ultra-violet light.

Investigating officers will be able to link suspects and any recovered cash directly to specific robberies by checking the tiniest speck against a central database.

Det Con Nigel Smith from the West Yorkshire Police Intelligence Bureau said: “The force has run a number of successful operations targeting criminals involved in cash in robberies and our efforts have seen the number of offences cut by nearly a quarter.

“Obviously that work is continuing and the introduction of this marking system will give a major boost to our investigations. It will be invaluable in helping us to track down those involved in cash-in- robberies.

“It gives us the ability to link suspects and any recovered cash directly to specific robberies.

“We are also convinced that its use by G4S across West Yorkshire will have a deterrent effect on those who commit these robberies.

“Anyone forcing open one of these cash boxes will be permanently marked as will the cash they have stolen.

“Police custody areas are fitted with UV lights that can detect the substance on anyone brought in and officers have been issued with UV torches they can use during their inquiries to check for traces on people or cash.”

Graham Hand, risk director for G4S Cash Services (UK) said: “Over the last decade the cash-in-transit industry has seen a marked increase in the number and severity of criminal attacks against couriers.

“This is just one of a number of proactive initiatives we are taking in association with West Yorkshire Police and other key stakeholders such as the British Security Industry Association to curtail the growing number of violent attacks taking place on the cash-in- industry.”