BRIDGEPORT - Bridgeport's police chief says he's tired of accused criminals going free because witnesses change their stories.

Bridgeport Chief A.J. Perez says he's lost two major cases this year because witnesses changed their stories on the stand.
     
Now, he's trying a new approach: bringing federal charges for violent crimes.

The most recent case was last summer's mass shooting at Trumbull Gardens in Bridgeport.
     
Police arrested Jamal Hamilton, but a jury last month cleared him of all charges.

All the victims testified they couldn't identify the shooter. Perez says that's not what the victims initially told police.
     
He says he's had enough of witnesses changing their stories.

In federal cases, witnesses have to testify before a secret grand jury.

Even if they change their story later, their testimony is already locked in and on record, and lying could land them in prison.