A Perth police officer who was suffering from undiagnosed post traumatic stress disorder (PTSD) because of his job has been jailed for almost two years for possessing images and videos of "explicit and depraved" sexual abuse of young girls.

Key points: David Mark Dodson possessed almost 350 images and videos of child exploitation

David Mark Dodson possessed almost 350 images and videos of child exploitation His lawyer said work-related PTSD made him 'obsessed' with pornography

His lawyer said work-related PTSD made him 'obsessed' with pornography The material included some of the worst categories of child abuse

David Mark Dodson, 29, was working as a detective in April this year when Canadian authorities discovered he had used social media to send an image to an unidentified person of a girl, aged between two and four, being raped.

Australian authorities then raided his home and found almost 350 images and videos of child exploitation material on his electronic devices.

The District Court was told the material included some of the worst categories of child pornography, featuring girls as young as two being abused by adults.

Some of the material were anime images, which are cartoon-like drawings that were described in court as being very realistic.

Dodson pleaded guilty to four charges and his lawyer, Mark Andrews, said at the time of his arrest his client was suffering from undiagnosed PTSD which was "a direct result of his occupation".

Dodson contracted PTSD during his work with the WA Police. (ABC News: Andrew O'Connor)

"He was a detective … and had attended death scenes, motor vehicle accident scenes and fights where he physically had to get involved … where his own life and wellbeing were put at risk," Mr Andrews said.

Mr Andrews said as "a coping mechanism" Dodson watched adult pornography for sometimes as long as eight hours after a traumatic day at work and he became obsessed by it.

He said Dodson continued to look for more hard core and better quality adult pornography, which led him to the illegal material.

"As he became more used to what he was seeing, he pushed the boundaries and that led him to child pornography … that was a by-product of his PTSD," Mr Andrews said.

'Police officers fear coming forward'

Mr Andrews said it was a tragedy Dodson had not sought help from his family or from the support services that were offered by the WA Police Force.

"I've acted for a large number of police officers who were affected by PTSD. The common theme is their reluctance to reach out for help because it's a stigma," he said.

"The average police officer appears to have a fear of coming forward."

Mr Andrews said Dodson was stood down on full pay after he was charged, but he had now resigned.

He said his client "suffered a profound degree of shame and embarrassment" and it was likely, because of his former job, he would have to be kept in protection in jail.

Prosecutor Tahlia Zerafa accepted that Dodson was remorseful and contrite for what he had done, but said the images depicted very serious child abuse.

Judge John Prior accepted that Dodson's offences were committed in the context of him suffering undiagnosed PTSD and his psychological state at the time did lessen his moral culpability.

But he said Dodson was a police officer with a distinguished career and it was his duty to uphold the law.

Judge Prior said some of the material was "explicit and depraved".

Dodson will have to serve at least 11 months in jail before he can be released.