Fingerprints are probably the absolute worst form of biometric identification. Under ideal lab circumstances or unconnected to actual humans, they're fine. Issue is that people use their hands on a routine basis. As others stated, skin is not very abrasive resistant. It's somewhat consistant day to day, but scars can become an issue at any moment. People get their hands dirty routinely.
Not to mention, I've never seen a finger print scanner that can read through blood. And I've asked every fingerprint scanner rep about that. They were uniformly horrified at the question.
"So, if I'm shot and bleeding, I get my hands soaked with blood from using pressure to reduce the bleeding, how do I open up this fancy fingerprint reader? If I use pressure to stop someone else's wound, or I was working on my car, or I was ripping up weeds, how do I open up the fingerprint reader?"
"You stop and wash your hands."
"So I have to carry around a sink, water and Gojo everywhere?"
"Er, yes."
"And if that pumice soap wears down my fingerprints a bit?"
"Er, you have to use the backup rekeying system..."
I wouldn't even trust fingerprint biometrics on my phone or tablet. Let alone on a safe, and certainly not on something mission critical like a firearm. Retinal pattern is usually pretty good, but generally too clunky to bolt to a firearm. They make rugged ones, but they're not small. Embedded RFID chip is probably the best option for size, reliability and speed. I'm sure police wouldn't object to getting chipped.
