The Australian radio station behind a hoax phone call to the London hospital where the pregnant Duchess of Cambridge was being treated could face criminal charges for airing the conversation, legal experts said Tuesday.

Last week's prank was widely condemned days after it aired, after the still-unexplained death of a nurse who answered the phone and helped two DJs get confidential information about the former Kate Middleton's health. But when it comes to a potential criminal case, the question is not about the death; it's whether a private conversation was broadcast without the permission of the participants.

Violators could be sentenced to prison, but it's unclear who at radio station 2DayFM or its parent company, Southern Cross Austereo, made the decision to air the call. The DJs have said executives above them made the decision, but a former 2DayFM host who orchestrated many pranks for the station said DJs were always involved in such decisions while she was there.

Southern Cross Austereo has said the station had tried five times to contact the hospital, but privacy law expert Barbara McDonald said that could prove to be an inadequate defence.

"Seems to me that saying, 'We tried to call,' shows that they knew they should, and they've made a decision to go ahead knowing that they have not got permission," said McDonald, a law professor at the University of Sydney. "I don't know whether it makes the situation better, or worse."

The New South Wales state Surveillance Devices Act prohibits the broadcast of recorded private conversations without participants' permission, with violations punishable by up to five years in prison and a fine of up to 55,000 Australian dollars, or about $57,000 Cdn.

McDonald said the Commercial Radio Code of Practice has a similar ban, but she added that even if Australia's media watchdog found violations, the most extreme punishment — loss of licence — is almost unheard of.

Australian authorities have said little about any possible investigation. State police have said only that they've been in contact with their London counterparts and are ready to assist them in any British investigation.

Nurse Jacintha Saldanha was found dead in her residence after she transferred a prank call from two Australian DJs asking about the Duchess of Cambridge's pregnancy. ((AFP/Getty))

Radio hosts Mel Greig and Michael Christian called London's King Edward VII Hospital last week. Pretending to be Queen Elizabeth II and Prince Charles, they asked for word on the Duchess of Cambridge, who had been suffering from severe morning sickness. Jacintha Saldanha, the nurse who answered the phone, put them through to the ward, and the duo received confidential information on the duchess' condition that was later aired.

The radio station trumpeted the prank call until Friday, when Saldanha was found dead. Police have not disclosed the cause of Saldanha's death, but many have assumed it was related to the stress from the call. An autopsy was to be held Tuesday.

Grieg and Christian tearfully apologized for the prank in televised interviews Monday, after days of condemnation in countless Internet posts around the world.

• Kate hoax call DJs tearfully apologize

Southern Cross Austereo also has apologized, and stopped running any advertising on 2DayFM following Saldanha's death. On Tuesday it issued a statement announcing that ads would resume Thursday, with all profits for the rest of December to be donated to "an appropriate fund that will directly benefit" Saldanha's family. The company said it would donate at least 500,000 Australian dollars (about $518,000 Cdn).

Austereo has repeatedly insisted that it followed the law. The company said in a statement Monday that the segment underwent an internal legal review before it was broadcast.

The company "does not consider that the broadcast of the segment has breached any relevant law, regulation or code," Austereo said, adding it would co-operate with any investigation.

On Monday, Austereo CEO Rhys Holleran said 2DayFM had tried five times, without success, to contact the London hospital to discuss the prank before it aired. The King Edward VII Hospital denied its management had been contacted by 2DayFM.

Media law expert Mark Pearson said that even if the station had tried to contact the hospital, that isn't enough under the law. He said permission must be granted by the person involved.

If the case went to court, it is possible that a judge could decide that an attempt at getting permission was sufficient, but only if the lawyers could prove that any "reasonable person" would agree that enough was done, said Pearson, a journalism professor at Bond University in Queensland state. He considered such a ruling to be a longshot.

Lisha Barboza stands with her father Ben while he holds a picture of his wife, nurse Jacintha Saldanha, as they leave the Houses of Parliament in London on Monday. (Dylan Martinez/Reuters)

"I think lawyers would be hard-pressed to argue that a few unprovable phone calls was enough to show that there had been a reasonable attempt to get permission," he said.

The case also could be investigated by the Australian Communications and Media Authority, the country's media watchdog. McDonald, the University of Sydney professor, said that stations found in violation generally are given warnings or told to train staff in proper procedures.

The authority has said it has received complaints about the hoax call and is looking into the case, but has not yet launched an official investigation.

Greig and Christian's comments Monday about higher-ups making the decision to air the call only raised more questions for Wendy Harmer, who hosted a morning show at 2DayFM from 1993 until resigning in late 2003.

Harmer said that when she was a DJ, she played an integral role in those decisions, and personally approved the many on-air pranks that she was responsible for.

The program producer, program manager and station manager needed to approve segments as well, Harmer said. She added that some segments were brought even higher to the group station manager for approval.

"If you're a DJ, and you're in front of the microphone, this is a very powerful medium and you should be absolutely apprised of all your responsibilities and all the rights of the audience," Harmer said. "And so to hear a couple of DJs who didn't seem to understand what those were was, I must say, alarming."

She added the company's statements that it had sought permission five times, and that the hoax call underwent legal review, are signals that the company knew "there's something big going down."

"I would say, 'If we have to bring the lawyers in, I'm not going to do it.' But I can say that with hindsight," she said.