L.A. Noire garnered a lot of respect for itself, not by its somewhat mediocre gameplay, but rather through it's impressive face capture technology. The tech was so impressive that you could literally tell any and every emotion a character was going through, even slightly. Seriously, even while playing the game, I often thought I was watching a detective drama on HBO.
It's that very same technology that makes this blooper reel that much more hilarious, and surreal at the same time. It's certainly not the first time anyone has ever done a computer generated gag reel. Toy Story had them in every movie. However those were all scripted sequences. L.A. Noire's real time face recognition allowed Team Bondi to capture these performances as they happened. Remarkable!
Though, whether the body animations were specially animated just for this sequence is questionable, the face reactions do seem to be spot on when it comes to life like reactions.