For decades, American courts have had to take it on faith that drug-sniffing dogs were impartial. Testimony by a dog's handler, along with training records and credentialing by a local K-9 organization, were usually enough. But the recent spread of body cameras now threatens to upend that faith.

A newly filed federal lawsuit in Texas shows cameras' potential to undermine K-9 unit legitimacy. Houston resident Alek Schott accuses Bexar County Sheriff's deputy Joel Babb of pulling him over on Interstate 35 on false pretenses, and then, when he refused to give permission to search his pickup truck, he says K-9 unit deputy Martin A. Molina III prompted his dog to "alert" to the scent of drugs.

K-9 handler body camera video from Bexar County, Texas. At approximately 1:00, the deputy's right hand is seen in the corner of the screen, gesturing. Alek Schott is suing the sheriff's office, saying that gesture prompted the dog to jump on the door, giving deputies the right to open the truck and search inside. No drugs were found. YouTube "These guys are trying to destroy my life"

Historically, that claim would have been nearly impossible to prove. But in this case, Schott requested and received the officers' body camera footage, giving him almost the same view the K-9 handler had — including the moment the handler's right hand made a gesture toward the attentive dog, which then jumped up on the pickup's door.

"It's clear to me that he's telling the dog to alert," Schott says. "I thought, 'These guys are trying to destroy my life.' "