Frankston Magistrates Court heard that Ross Hewitt, 33, called police at 1.54am on July 28 last year to report a fictitious car accident on the Nepean Highway, Seaford.

After arriving, police realised there had not been an accident and saw Hewitt standing behind a letterbox, drinking from a can.

When police officers searched Hewitt, they found two empty syringe packets and a pen pistol up his left sleeve.

Hewitt told police he had purchased heroin and the pistol in Springvale and admitted calling police to the scene.

Hewitt's lawyer Effie Lagos said although her client had abused numerous substances from the age of 13, he suffered no mental health problems as a result.

Ms Lagos said Hewitt's brother and father had died and he had been assaulted with a metal pole which "might explain his need for protection".

She said his paranoia was exacerbated by drugs and he had consumed alcohol and heroin before calling the police.

Ms Lagos said her client had not taken drugs in the past six months, did not know how to operate the pistol and had made no attempt to use it.

For possessing a prohibited weapon and carrying it in a populous place, and for possessing ammunition without a permit, magistrate Franz Holzer sentenced Hewitt to four months' imprisonment, with a term of one month to be served.

Hewitt was fined $800 for making a false report to police, $1300 for possessing various drugs and $500 for possessing ammunition without a permit. Hewitt is also serving prison time for matters relating to theft and drug possession in 2010.

"You are a person who has taken steps to address your behaviour but the repetitious nature of the offending, the constant use of drugs and the totality of the offending means there is a real community concern," Mr Holzer said.

Ms Lagos indicated she would appeal the sentence.