LANCASTER, Calif. >>  Los Angeles County sheriff’s officials say they arrested a man suspected of groping a woman in her home by tracing DNA on the flip-flop slippers he left outside her apartment to avoid detection.

Sgt. Mark Machanic says 20-year-old Christopher Prather was charged Friday with burglary and sexual battery for entering the Lancaster apartment of a 21-year-old woman in the early hours of Feb. 11.

Machanic says Prather watched the victim sleep until she woke up, whispering “excuse me” before he groped her and fled.

When the flip-flops were discovered they were sent for testing and linked to Prather, who is currently on felony probation for robbery.

Prather was arrested Tuesday, hours after lab results were returned to Lancaster officials.

He is being held on $170,000 bail