NASHVILLE, Tenn. (WKRN) — Two officer-involved shootings in Nashville on Friday, one resulting in the death of a woman, had one thing in common: The officer’s tasers appeared to fail.

While tasers are often an officer’s first line of defense to get someone to comply, experts tell News 2 there are many times they don’t work.

Footage of both shootings from the Metro Nashville Police Department’s new body cameras reveal this may have been the case in both incidents.

In Friday night’s officer-involved shooting in Goodlettsville, the footage clearly shows one of the taser’s two darts misses the woman who is wielding a pick axe and baseball bat.

“If it’s in, the darts are in the clothing of the person or in the skin, you’ll see the person react to it and generally the reaction as they fall over and do what you say,” said Bob Allen, a former MNPD officer for 35 years, 23 of which he trained cadets.

Allen is now the director of training at Royal Range USA in Nashville, training in self-defense and weapons.

Friday morning’s officer-involved shooting in North Nashville showed the officer shooting the taser darts at the woman repeatedly, yet she never appears to stop moving.

Allen says a taser will only work effectively if both darts land not only on the target, but on areas of the body that have larger muscles in order to induce the involuntarily muscle contractions that will cause a person to go limp or fall over.

“I remember using it on a recruit, and it was into the back,” Allen recalled, “One dart hit him in the lat muscle, the big muscle on your back and the other one hit it in his wallet…. so, it didn’t work for him.”

If the darts don’t catch muscles, an officer can also use the taser directly on someone’s body, which we see the officer do in video from North Nashville.

“Touching (is) what’s called pain compliance,” Allen explained, “So if it’s painful to you, you obey what I’m saying. But if you’re geeked up, on cocaine or PCP, mentally off a little bit, then this is not very painful and they can just knock it off.”

Unfortunately, even pain compliance did not work on the woman and she was ultimately able to grab a gun and shoot the officer in the torso, prompting a brief shootout that ended her life.

The axe-wielding woman was also shot, but is recovering.

“The only time officers pull a handgun is when they think their life or somebody else’s is in danger… Whether the taser is effective or ineffective it doesn’t mean I get this out,” Allen explained pointing to his gun, “That all determines on what the person we’re trying to arrest does. So, if they get at you with an edged weapon and come at you, then we drop the taser and get a handgun out.”

News 2 asked MNPD about the tasers used in those two shootings and whether they were functioning, but they did not have a response.

The Tennessee Bureau of Investigation is the lead on both shooting investigations.