HALIFAX -- Defence lawyers for two teens accused of child pornography in the Rehtaeh Parsons case said Wednesday they want a senior Crown prosecutor to explain why, days after her death, Nova Scotia's Public Prosecution Service changed a policy allowing it to lay charges in offences involving sexting.

But the Public Prosecution Service said there was in fact no policy on sexting -- the sending of sexually explicit images and words via text messages -- before the 17-year-old girl died last April.

Defence lawyer Ian Hutchinson has filed a subpoena to have Crown prosecutor Craig Botterill testify, and the application is supported by the other defence lawyer in the case, Brian Church.

A lawyer for Nova Scotia's attorney general has filed an application to quash the subpoena, saying it would breach client-solicitor privilege.

That application contains an email from Hutchinson that lays out the defence's position. In the email, Hutchinson says if the prosecution service's policy hadn't changed a few days after Parsons' death, child pornography charges wouldn't have been laid against the two teens.

"It is understood that the Nova Scotia Public Prosecution Service administrative policy and procedure relating to 'sexting' offences which were in place during the initial police investigation are different from the current policy," Hutchinson says in the email to the Crown.

"Had the 2011/12 policy been followed I understand the Crown would have withdrawn both charges against my client."

Hutchinson said Wednesday that the prosecution service's policy in 2011-12 was that if a youth took a sexual picture of a youth of a similar age, charges wouldn't proceed.

But Chris Hansen, a spokeswoman for the Public Prosecution Service, said there was no policy on sexting prior to Parsons' death.

"The sexting policy was the first such policy we ever had," she said in a phone interview.

"There was nothing before that. The Parsons case identified a gap we had in our policy manual and we filled that gap."

In provincial court, Hutchinson said a senior Crown attorney can be compelled to testify when there is a possibility of misconduct by the Crown. He didn't specify what Crown misconduct was possible.

Church told the court that Botterill's testimony would help it understand why charges were laid against the teens, who are now 19 but whose identities are protected by a publication ban because they were minors at the time of the alleged offences.

"It may be possible it will assist the court in determining, in the future, whether there was an abuse of process," said Church.

"While it's not a fishing trip, we represent the accused young people and we don't know why the charges were laid."

But Alexander Smith, the Ontario prosecutor handling the case for the Crown, told the court the subpoena should be quashed.

"It's the Crown's position that Mr. Botterill has no relevant evidence to give," said Smith.

"My friend is simply trying to launch into an abuse of process application attacking Crown discretion, without providing any basis for doing so."

Provincial court Judge Jamie Campbell adjourned the hearing until next Wednesday, when he'll hear further arguments on the application to quash the subpoena.

Parsons was taken off life-support following a suicide attempt last April. Her family says the 17-year-old girl was bullied for months after a photograph of her allegedly being sexually assaulted in November 2011 was passed around her school.

Shortly after Parsons' death, the Public Prosecution Service said police approached them in October 2012 to determine if there were reasonable grounds to lay charges and secure a conviction. But the prosecution service said at the time they concluded there was no realistic prospect of conviction because of insufficient evidence.

A week after Parsons died, police reopened the investigation, saying they received new information.

The two teens were charged last August with distributing child pornography, while one is also charged with making child pornography.