Police have revealed that the notorious murders of two young Sydney girls half a century ago could be solved through improved DNA technology.

The girls, Marianne Schmidt and Christine Sharrock, were horribly killed at Wanda Beach and buried in shallow graves in the mid-1960s.

Dubbed the "Wanda Beach Murders", it is one of the thousands of cold cases - some decades old - that police now say they may be able to solve due to technological advances in DNA.

Police say a bloodstain has recently given a weak DNA match, but it will be several more years before the case could move forward.

On January 11, 1965, Marrianne and Christine were both stabbed, and Christine had her throat slashed.

In an ABC archive tape which was made in late January 1965, two weeks after the murders, an ABC reporter spoke to Detective Inspector Haynes, who was leading the investigation.

"We feel that this man is a compulsive killer who must stab and have sexual intercourse with his victim as an overall part of the act. We feel that if he is not caught soon he will act again," Mr Haynes said

When asked if he thinks he will ever catch the murderer, Mr Haynes replies: "We feel that we will eventually get this man."

But 47 years later, police are still hunting the killer.

Superintendent Mark Sweeney, who was a young boy when the girls were killed, is now a forensics police officer who is investigating the case.

"We had two young girls...who were victims of a homicide, that actually turned the psyche of Sydney on its head at the time," he said.

"Recently in the last 15 months a number of items have been examined arising from the Wanda beach murders."

One of those items was a pair of jeans worn by one of the two girls when they were killed.

There is a bloodstain on the front of those pants that did not yield any clues at the time.

Now a new DNA test of the bloodstain has given what is termed a "weak" identity clue.

"We understand that it is a male profile. But at this point in time, as I speak, we are unable to progress," Mr Sweeney said.

Police admit the current technology is not good enough to give a more specific identification, but they do know the girls were last seen with a teenage boy.

Bond University criminologist Wayne Petherick says some of the advances that have come about are in better machinery that can reproduce DNA.

"When you get a DNA sample, if that sample is small, you have to use a machine to effectively amplify the amount of DNA you have to test," he said.

He says time passing may help cold case policing in another way.

"After a period of time people might be more likely to come forward about the crime that's occurred," Mr Petherick said.

"For example, back in the day they might have been scared of the perpetrator - they knew who did it, but didn't want to say anything because of fear they themselves would get harmed.

"Perhaps the perpetrator's since died so they can come forward with information now so the crime can be closed...so some things just get better with time."

View post:
DNA advances may solve brutal murders