Jordan David Hans Gill also used items he bought on eBay to dress as a police officer, before posting pictures of himself in the fake uniform on social media.

Gill, who also goes by the name Jordan Fristad, appeared in the ACT Magistrates Court on Wednesday.

He had earlier pleaded guilty to charges of impersonating a police officer, using a carriage service to threaten, and intimidating a Commonwealth official.

Prosecutor David Bloomfield told the court Gill had sent 11 threatening emails to a police officer between October 2 and October 8 last year.

Mr Bloomfield said the emails contained "substantial abuse" about the officer's weight, state of health and ability to do his job. There were also references made to the victim's family.

He said the threatening emails were aggravated by the fact Gill had previously committed firearms offences, which the victim would have known about, and that the victim had cause to believe Gill's fixation with him might lead Gill to try and track down his family.

"There was a means and possibility of [the threats] being carried out that was beyond remote," Mr Bloomfield said.

He said jail time was the only appropriate sentence to denounce the threats and send a message to the community.

But defence lawyer Todd Trotter said at the time Gill sent the emails, his firearms licence had been cancelled and his gun was locked away in the police exhibit management centre.

Mr Trotter said Gill had pleaded guilty at an early opportunity and shown "palpable remorse" for the threats, which he acknowledged would have been distressing for the officer.

He said Gill was "absolutely spiralling out of control" when he sent emails from his personal account, which clearly showed his name, to the victim's police email account.

While "horrible" offences, Mr Trotter said they had been the trigger for Gill to address his mental health issues, which he had since done.

Mr Trotter said placing Gill back in custody, where he had spent 47 days following his arrest, would undo the progress he had made since being granted bail in November.

"They were a call for help," Mr Trotter said of the threatening emails.

"[They were] a very poor one, but if he had friend at that time - someone that he could have unloaded to - maybe we wouldn't be here."

Mr Trotter said there was no malice involved in the incident in which Gill dressed as a police officer and posted pictures to social media.

He said Gill had not attempted to exercise power over anyone or put anyone at risk by pulling this stunt, which was "a very poor form of self-protection".

Mr Trotter said Gill was effectively telling people he believed were stalking him: 'Don't mess with me, I'm AFP'.

"At worst, it can be seen as an ego boost for social media," Mr Trotter said.

Magistrate James Stewart said he did not believe the impersonation charge warranted time behind bars, but only jail sentences would be appropriate for the threats.

Mr Stewart adjourned the case and said he would hand down sentences next Friday.