A Quebec judge has acquitted an HIV-positive Montreal man accused of sexually assaulting a woman with Down's Syndrome after she failed to positively identify her attacker.

Serge Levac was acquitted Thursday of four charges: aggravated sexual assault; sexual assault with a weapon; break and enter; and uttering death threats. The alleged victim for all the charges was a 47-year woman with a mild case of Down's Syndrome.

Quebec judge Patrick Healy said he had no doubt the woman was telling the truth about being attacked and assaulted on Oct. 2, 2008, but while evidence against Levac was strong, it wasn't sufficient to dispel any reasonable doubt.

Healy called the assaults "brutal" and said Levac probably committed the crimes but that probably is not good enough under the law.

Crown attorney Patricia Compagnone said she'll take some time to decide whether to pursue the case any further.

Levac was arrested Oct. 5, 2008, and in January, police issued a public call asking for help to identify any other potential victims in part out of fear that Levac's HIV status could pose a public health risk were he found to have committed sexual assaults.

At the time, police said Levac met his alleged victim while volunteering at a community organization that works with people who have mental disabilities. Investigators said they believed he might have preyed on others as well.

With files from The Canadian Press