Pc Stephen Norman at Aylesbury Crown Court

Steve Norman, 44, was charged after Emily Higson, 22, died during a night out in Oxford last November.

Pc Norman admitted travelling at between 50mph and 60mph as his patrol car, which had lights and sirens on, responded to an emergency call.

On Monday the judge ruled the Crown had not produced enough evidence to prove Pc Norman had been driving dangerously.

Pc Norman, who denied a charge of causing death by dangerous driving, had overtaken another vehicle shortly before the accident but Mrs Justice Rafferty said "no inherently dangerous manoeuvre" had taken place.

Miss Higson's father, Dr Roger Higson, said the family would have difficulty accepting the outcome.

He said: "We are concerned that, unless urgent steps are taken, the same tragic, senseless and preventable loss of life will occur again."

Braked and swerved

Miss Higson, who was studying sociology and anthropology at Oxford Brookes University, had been drinking with friends at Baby Bar on Cowley Road.

She did not wait for the lights to turn before attempting to cross the road, the jury at Aylesbury Crown Court heard.

Pc Norman said he did not see Miss Higson until she was 10 or 15 metres away.

He braked and swerved but she was hit and thrown 24 metres through the air.

Miss Higson died at the John Radcliffe Hospital the following morning.

Pc Norman has been off sick since the incident but is expected to return to work, a police spokeswoman said.

She added that discussions will take place about whether he should resume his driving duties.