Smaller pellets also don't penetrate flesh deep enough to reach the vital human organs.
^^^^ This was #3s or #4s from 15-20 yards. And he's still walking around, none the worse for tear.
Different vic, same result. Still alive and kicking.
It's stupid to get so wrapped around the axle about what the consequences of shooting through a wall might be if leads you to make decisions that prevent you taking care of job #1, neutralizing the threat.
Leave birdshot for the birds and use buckshot on humans, nothing smaller than #1s. And no, #4 buck WILL NOT do the business unless you're buying plated or hardened shot.
https://gatdaily.com/articles/just-say-no-to-number-4-buckshot-for-home-defense/