Johnny Manziel's Mom Failed Field Sobriety Test, Refused Breathalyzer Before DWI Arrest

Johnny Manziel's mom refused to take a Breathalyzer and failed a field sobriety test just before she was thrown behind bars last week for DWI ... law enforcement sources tell TMZ Sports.

Michelle Manziel's run-in with cops took place in Kerrville, Texas at around 10 PM on March 1 ... after we're told Kerrville Police Department officers noticed she was driving with a busted tail light.

During an ensuing traffic stop, our sources say Michelle showed signs of intoxication ... including blood shot, glassy eyes and unsteady balance. They also claim Manziel's mother had a strong odor of booze emanating from her breath.

We're told Michelle refused to take an intoxilyzer test ... and when authorities administered the horizontal gaze nystagmus check, she showed six clues of inebriation.

The 55-year-old was taken to a nearby jail, booked on a DWI charge ... and later released on $7,500 bail.

Michelle's attorney told us Friday morning they have no comment on the matter.

Johnny, meanwhile, has not kept a low-profile in the wake of his mom's arrest ... he was just seen at a Texas A&M men's basketball game laughing it up with Mike Evans.