A former Department of Child Protection worker has been sentenced to 16 months' jail for grooming and showing indecent material to local children in far-north Western Australia.

Key points: Rasmussen, 31, showed a video to a group of five children depicting a naked man slapping his penis

Rasmussen, 31, showed a video to a group of five children depicting a naked man slapping his penis Weeks afterwards he began messaging and grooming what he believed to be a 14-year-old girl online, encouraging her to masturbate and sending photos of his erect penis

Weeks afterwards he began messaging and grooming what he believed to be a 14-year-old girl online, encouraging her to masturbate and sending photos of his erect penis Rasmussen was sentenced to 16 months jail for for grooming and showing indecent material to children

Corie Keld Rasmussen, 31, faced the Kununurra District Court on Monday charged with several child sex offences, five of which occurred while he was employed as a care worker for vulnerable children.

Prosecutor Danielle Clarke told the court Rasmussen was working at the department's care facility in Kununurra last July when he showed a video to five children, one as young as eight, that depicted Toy Story characters and a brief clip of a naked man slapping his penis with his hand.

Defence lawyer Ben White said his client had a simple lapse of judgement and showed the video to make the children laugh.

He pleaded guilty to the charge at the earliest opportunity and was released on bail, but the Court heard Rasmussen committed more serious offences just weeks afterwards.

Explicit images sent to 14-year-old 'persona'

The court was told Rasmussen had started messaging what he believed was a teenaged girl over Facebook, after she initiated contact and they became friends.

On August 18, she informed him she was only 14 years old, at which point the conversation turned sexual shortly afterwards.

Rasmussen's messages encouraged the girl to masturbate and asked her to send photos of herself.

On the same day, he sent her a photo of his erect penis.

Ms Clarke said it was clear he had an interest in children and there was an element of grooming involved.

Rasmussen was charged again, this time with using electronic communication to expose a child under 16 years to indecent matter, and using electronic communication with intent to procure a person under the age of 16 years to engage in sexual activity.

Mr White said his client was left feeling socially isolated after the negative attention he had received on social media following the first set of charges.

Strong case for the prosecution

Judge Christopher Stevenson noted that the victim in the August offences was a "child persona" and not an actual teenaged girl.

It was not publicly stated during Rasmussen's numerous court appearances who was portraying the teenager.

But Judge Stevenson said it was in no way a mitigating factor and that Rasmussen believed he was messaging a 14-year-old girl.

While Rasmussen had pleaded guilty to all charges at the first opportunity, Judge Stevenson said he doubted whether he had any real remorse or insight into the seriousness of his behaviour.

Five reference letters were also presented to the court in support of Rasmussen, but the Judge noted that at least two were written prior to the August offences and the authors may not have been aware of the seriousness of Rasmussen's offences.

Well known in the community

Sentencing Rasmussen, Judge Stevenson noted the man's history of volunteering and community involvement.

He also drew on the psychological report, which the primary protective factor that could stop Rasmussen from re-offending was the fact he was in a long-term relationship with his girlfriend of a similar age.

The psychological report said the pair's relationship had strengthened following the August charges.

He said while the July charges alone may have warranted a suspended sentence, the seriousness of the August offences and the fact her was on bail at the time meant immediate imprisonment was the only option.

Rasmussen will be eligible for parole.