When is the moment that Gerard realized Kimble was innocent?

... he still tries to shoot him dead as he's escaping from the government building, a scene that left me scratching my head.

I like that we aren't quite sure where Gerard stands on Kimble, who is his prey after all, until the end. It creates a tension if you think Gerard is capable of killing the fugitive at any point.

I agree Benoit. I think Sam had suspected Richard's possible innocence from the moment he realized Richard was searching for the one-armed man, and the phone call evidence confirmed it for him.

If you notice in the scene, he naturally immediately requests Sykes be brought in for questioning, but also quickly goes to view the arrest report. This report must include far more information than the reports one can find online at the CPD website because Gerard's report most likely includes a timeline of the night Helen died, which indicated when Richard arrived and left the fundraiser. Once Sam realized Richard couldn't possibly have made the call, he knew for a fact Richard was innocent.

That's how I read it as well.

There was also one crucial piece of circumstantial evidence: the murder of Mrs. Richard Kimble was a savage one, with little regard to the victim.

Compare that with risking life and limb saving an unrelated child, using his vast medical knowledge, pretty much screams "not a person a single minded track of lunacy". It does require the focus and empathy, that was totally void, when his wife was murdered. Since the local cops offered motive as premeditated murder to commit insurance fraud, this action is way out of character for a cold and calculating person.

One other thing, as shown by the capture of the other criminal who went back to his baby mama, fleeing criminals, especially hardened ones have a backup plan. Richard was the only convict, who, despite being rich, had no tucked away stash to just begin a new life, which is, yet again, very strange for a supposed cold and calculating murderer, the type Gerard used to deal with.

I live in the Gordius Apartment Complex, my interior designer was M.C. Esher.