A backdated non-parole period that Magistrate John Chicken handed down yesterday as part of the punishment meant that the 36-year-old would have been immediately eligible for release - but for separate serious drug supply charges making their way through the courts, which have kept him behind bars since early this year.

Musgrave was charged almost three years ago after a spree in the Windale area during which he set fire to piles of rubbish that had been put out for collection - including several mattresses, clothing and skip bins.

According to a statement of agreed facts tendered to the court, Musgrave was seen in dark clothing riding around the area on a pushbike when the fires broke out.

It came about a week before he torched four vehicles - a Ford Focus, a Toyota Corolla, a Ford Fiesta and a Holden Viva - which were parked together at a Windale unit complex.

Court documents said witnesses "saw each of the four cars had been set on fire" after hearing an explosion.

When asked during an interview with police why he started fires, Musgrave said "it's something that I need to, like, get help with" - though he denied having a fascination with fire.

In Belmont Local Court on Monday, Magistrate Chicken sentenced Musgrave to a three year prison term - including a 25 per cent discount for his guilty pleas.

Magistrate Chicken ordered a non-parole period that was backdated to take into account time he already spent in custody and which ended immediately.

He found special circumstances in the psychological profile prepared in the lead-up to sentencing, which deemed Musgrave to have experienced a major depressive disorder before the fires.

But Musgrave was to remain behind bars last night, with the court hearing that he had been re-arrested in February and charged with what Magistrate Chicken described as "some significantly more serious [alleged] offences" when police allegedly found him in possession of 401 grams of methamphetamine - which had an estimated street value of more than $360,000.

He will face court over those charges on Wednesday.

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