A retired Chatham music teacher, who was found not guilty of sexual assault last year, must return to court after an appeals panel issued convictions in his case.

The provincial appeals court has ruled the judge who presided over the case of Claude Eric Trachy "erred in law" by acquitting Trachy of 51 sexual assault and indecent assault charges last April.

A three-judge appeals panel released its decision on Tuesday, issuing convictions on 28 charges.

Trachy was charged in 2015 after Chatham-Kent police received 25 complaints.

Trachy, now 73, had been teaching violin for more than 50 years

During the trial, court heard from female students who claimed Trachy touched their breasts and had them remove their blouses and bras during lessons in the 1970's and 80's.

Trachy claimed his actions were to measure students to fit them for violin shoulder rests.

Justice Thomas Carey accepted Trachy's explanation, ruling in his favour.

The crown appealed that decision in May, arguing the judge "brushed over" major evidence and did not take into account the complainants suffering.

Two counts have been set aside because of the complainant's age at the time. Acquittals on sexual exploitation and sexual interference charges will stand.

The appeals panel also requested a different judge to determine sentencing.