Peter Charles Henderson, aged in his late 30s, had pleaded guilty to using a carriage service to transmit child abuse material and possession of child abuse material.

In the ACT Court of Appeal last week, Justice Chrissa Loukas-Karlsson, Justice Verity McWilliam and Justice Belinda Baker ordered Henderson spend nine-and-a-half months behind bars, before entering into a two-year good behaviour order.

In May 2023, Acting Justice Stephen Norrish had sentenced the man to a total of two years and four months in jail, with 10 months of those to be served in custody.

Henderson was due to be released in March 2024 but walked out of jail last week.

Henderson has admitted to sending 68 child abuse files and text-based abuse material to co-offender Chelsea Amalia Crivici via WhatsApp.

The pair first met on Tinder with the offences occurring between October 2021 and March 2022.

Crivici previously said she was trying "to play cop" and surrendered herself to police after keeping the files "as evidence".

Henderson was also found with almost 2000 child abuse images and videos.

The files showed 1000 individual child victims, largely aged between one and 10.

In a judgment published on Thursday, the Court of Appeal found acting Justice Norrish had erred in sentencing Henderson on the basis he had the child abuse material for more than one day and using this evidence as a "circumstance of aggravation".

The judge also made a mistake in finding "exceptional circumstances" must exist before an intensive correction order could be imposed.

During a hearing, Henderson gave evidence that he had received "constant threats" from another inmate while in jail.

These threats were directed at Henderson, his dog, and his housemate, including reciting his residential address.

In July 2023, Henderson claimed he had a verbal exchange with the other prisoner, who grabbed him and then threatened him not to report.

The next month, the inmate punched Henderson in the head twice.

On another occasion, the other prisoner followed Henderson into the laundry, out of the view of CCTV cameras, and pushed him.

When Henderson reported the assaults to prison authorities, a regime was imposed where the two inmates were confined to their cells for opposite halves of the day.

The appeal judges found "the hardship experienced by [Henderson] was not significantly different to that experienced by other offenders who are sentenced to a period of imprisonment".

However, the judges had "considerable doubts" about Henderson's claims his crimes were not sexually motivated.

"Regardless of the appellant's motive, these offences occasioned serious harm to many victims, all of whom were very young," the judgment states.

In May, acting Justice Norrish had described the child abuse files as "so disgustingly depraved it is almost impossible to derive of any person who would take any pleasure or interest [in it]."

"One of those files is so horrific that standing by itself it represents an extreme," the judge said.