BURGLARS and thieves could hold the key to trapping a balaclava-clad rapist who has attacked several pensioners in their homes.

DNA samples taken from 2,500 known burglars and other men who fit the description of the attacker will be compared with samples taken at the scene of seven of the crimes.

The man raped four women aged between 65 and 92, and broken into the homes of several others, indecently assaulting some.

Officers believe the man is a skilled burglar who picks victims from key areas in south east London including Orpington, Sidcup, Catford and Forest Hill.

DCI David Zinzan said: So far only about 12 per cent of the men asked for a sample have refused because this is a crime even hardened criminals find abhorrent.

The victims are often frail and need extensive medical attention after the attacks and, because of their age, never fully recover.

Almost 1,500 men have already been eliminated from the investigation.

DCI Zinzan said: We want to let people know this mass swabbing program is going on and assure them the samples taken will only be used to eliminate people from this investigation and then destroyed.

Once someone agrees to be tested, a mouth swab is taken.

Basically a swab looks similar to a cotton bud, but will be rolled on the inside of the mouth and the sample will be sent of for testing.

He hopes the new publicity will deter the rapist from striking again as he increases his activity in December. He attacked one 77-year-old Orpington woman on Christmas night in 1998.

The first attack occurred in February 1992, in Forest Hill and his most recent victim was an 87-year-old living in Shortlands, Bromley, in April.