Internal affairs detectives are investigating a crash in Southern River yesterday afternoon which left a motorcycle rider in a critical condition.
About 4.30pm on Garden Street, police officers in an unmarked car noticed a motorcyclist approaching them from behind at speed.
Police spokesman Sam Dinnison said the officers activated their emergency lights as they were overtaken by the motorcyclist.
He said the rider appeared to slow down at first, but then sped out of sight.
As the officers mounted a crest they saw the motorcyclist drive through a red light at the Warton Road intersection and collide with a white Volkswagen Tiguan.
The man was thrown from his motorcycle, sustaining serious head injuries.
He was taken to Royal Perth Hospital where he underwent surgery and remains in a critical condition.
The driver of the Tiguan suffered shock and was taken to hospital for treatment.
Mr Dinnison said internal affairs detectives and major crash officers were investigating.Anyone who saw the crash is urged to call Crime Stoppers on 1800 333 000.