But the Crown has launched a simultaneous appeal against a two-year jail sentence for home invader Drew Francis Thompson, 28, saying it was "manifestly inadequate".

Thompson met the victim on dating site eHarmony in March 2013, but the pair split after a short relationship.

The woman publicly humiliated him, calling him boring and stupid, after he persisted in trying to win her back.

Thompson, the Crown alleged, then formed a plan for revenge, writing in a note that he had wanted to show her how damaging it was to break someone's trust.

He took an unloaded gun and entered her apartment, hiding and waiting for her to come home. He then sprung out, put a gloved hand around her mouth, and told her not to scream.

He threw her to the bed and rested a gun on her chest.

Thompson then kept her in the apartment for three hours.

He was found guilty at trial of unlawful confinement and aggravated burglary, and was sentenced to two years imprisonment, to serve eight months.

Now, Thompson has appealed against his conviction.

The appeal revolves around the presence of a witness assistant with the victim as she gave evidence in a remote room via video link, usual practice for such crimes in ACT courts.

Thompson's barrister Stephen Odgers, SC, argued the law required the judge to warn the jury not to draw any adverse inferences against the accused because of the fact the victim was being assisted by a support person.

That is done to prevent the jury from lending more weight to the allegations and to remove any prejudice they may feel against the accused attacker.

Mr Odgers pointed to a number of decisions in Queensland, which he said had reinforced the need to warn the jury in such circumstances.

He said ACT law required judges to do the same in this jurisdiction.

"The legislature of the ACT has imposed an obligation on the judge ... and the obligation is to say something to the jury," he said.

But Director of Public Prosecutions Jon White told the ACT Court of Appeal on Wednesday that the witness assistant was not even pictured in the video link to the remote room, and the jury were not told of her presence.

Mr White argued the witness assistant did not meet the definition of a support person physically present in the courtroom, meaning there was no requirement on the judge to give any warning to the jury.

"There really is zero effect on this trial by the fact that there was a person sitting off-camera," he said.

"There is no effect ... none whatsoever."

Later on Wednesday, the Crown appealed against the two-year jail sentence handed to Thompson by the ACT Supreme Court.

Mr White said it was inconsistent with other sentences for less serious, residential-type burglaries, pointing to one such case where a man broke into a property to steal goods and had a confrontation with the residents.

The starting point in the case was four years behind bars.

"We say that the current case is far more serious, far more significant than that scenario," he said.

Mr White said the sentencing judge did not give proper weight to the serious circumstances of the case, including the emotional scarring to the victim, the lengthy confinement, the pre-meditation, the use of gloves and the gun, and the fact it happened in the victim's home.

He argued the sentence needed to deter others from similar crimes, particularly because it occurred in a domestic violence context, and in response to a break-up.

But Mr Odgers argued the sentence was appropriate, saying there was no error of principle.

He said the case was "quite unusual" and unique, meaning there were no sentences it could easily be compared to.

The judge, he argued, took into account all of the circumstances of the case when delivering sentence, and also made favourable findings to Thompson about his mental health and prospects for rehabilitation.

"Given these favourable findings, there was nothing clearly unreasonable about this sentence," he said.

A full bench of the ACT Court of Appeal, comprising Justices John Burns, Richard Refshauge, and Darryl Rangiah, has reserved its decision.