TORONTO - Attorney General Chris Bentley says an investigation is underway after a prosecutor's strange behaviour in a Toronto court prompted a judge to declare a mistrial.

The Crown prosecutor reportedly distracted and upset the jurors by making faces during the testimony of Erika Mendieta, who is accused of killing her one-and-a-half-year-old daughter Emmily.

It was Mendieta's second trial, as her first trial ended with a hung jury last year.

The jury sent a note last week to Justice Nola Garton asking that the man sitting in the front row -- who turned out to be Crown counsel Paul Alexander -- be removed from the court because he was distracting them.

Bentley says the chief prosecutor is investigating the matter, but wouldn't say whether Alexander -- who helped prosecute Mendieta during her first trial -- would face any disciplinary action.

But NDP justice critic Peter Kormos says Alexander "screwed up" a serious trial that was close to completion and should find another job.