A judge in the Guelph trial of Cory Armishaw has found the defendant not guilty of second degree murder after ruling his rights were violated.

The decision comes just hours after the judge ruled a statement taken by police, a confession, was involuntary and should be excluded.

Twenty-six-year-old Armishaw was accused of killing his then girlfriend's almost three-month-old son by shaking him in November of 2006. Medical experts say the child was violently shaken.

Armishaw reportedly told an OPP detective that he shook the infant, but the nature of the interrogation and confession were brought into question.

Defence lawyers argued that during an interview with police Armishaw was questioned relentlessly despite invoking his right to remain silent at least four times on the advice of his lawyer.

Defence lawyer Craig Parry says "The defence took the position that the tactics employed in interrogating Mr. Armishaw were dangerous, that they have the great danger of creating false confessions."

Armishaw was also told there was forensic evidence against him, when there was none.

Parry says "Coupled with that there's the use of false evidence which gives the person the impression there's no way out. You get to choose between being a cold-blooded killer or a nice guy who snapped."

The interrogation was conducted by OPP Det.-Sgt. Jim Smyth, who was once praised for getting a confession from convicted murderer Russell Williams.

On Monday the judge agreed with the defence's claim that the statement was involuntary and that Armishaw's rights to counsel were violated.

The statement was considered crucial to the Crown's case, and following the exclusion prosecutors told the judge they had no reasonable prospect of conviction and asked for an acquittal.

Crown prosecutor Pam Borghesan says "The difficulty in this case was that the viability of the prosecution depended on the confession. Without it there's no prosecution."

The judge then placed a not guilty ruling on the record.

Borghesan's thoughts remain with the child's family. The boy would have been five years old.

"I hope that this might enable them to put this chapter behind them and just move ahead with their lives."