But a Canberra magistrate declined to convict Domaneco Zizi, 86, for animal cruelty, as she had seen no evidence of the harm suffered by the possum.

The ACT Magistrates Court heard on Wednesday that Mr Zizi had previously fed the possum in his backyard, but then attacked it with a pole when it attempted to enter the roof cavity of his Woden home by crawling along a power cable.

Neighbours filmed the violent incident about 3pm on October 25 and handed the footage to the RSPCA.

The disturbing footage – which was played in court on Wednesday – shows a two-to-three metre piece of PVC pipe striking the possum about 12 times as it clings to an electrical wire near a home.

The native animal – which is a protected species – then loses its grasp on the wire and hangs on by its tail, where it is then struck a further four times until it falls out of sight.

Mr Zizi's lawyer, Jessica Vogel, said her client denied striking the animal once it fell to the ground.

Mr Zizi pleaded in the Magistrates Court to cruelty to animals.

A charge of aggravated cruelty was dropped by prosecutors on Wednesday.

The court heard the grandfather was a loving and dedicated family man who was "deeply ashamed" of his actions.

Ms Vogel said the attack on the helpless animal, while inexcusable, been a compulsive act to prevent it from entering the roof cavity of his home.

The lawyer said Mr Zizi's family members had previously had damage caused to their property by the native species, and he feared a repeat in his own home.

The court heard he was the sole carer of his 90-year-old wife and struggled to manage both the housework and her needs as his own health deteriorated.

Character references, tendered on his behalf, described the attack as "out of character".

Ms Vogel asked the court to grant the octogenarian a section 17 - which would allow him to avoid conviction on account of his good character.

But prosecutor Soraya Saikal argued the courts needed to send a strong message to the community that animal cruelty would not be tolerated.

Ms Saikal said the offence had been low-to-mid range, but had been a cruel attack on a "completely harmless" animal.

Magistrate Beth Campbell described the incident as "unpleasant conduct", but said the court had seen no evidence of harm or injury caused to the possum.

The magistrate said the case was not an appropriate vehicle for general deterrence because of Mr Zizi's subjective circumstances, including his age and crime-free life.

Ms Campbell declined to convict Mr Zizi, but ordered he sign a one-year good behaviour order.