There are several issues here
1) Whether or not humans are completely described by the laws of physics. That is, is there nothing beyond the material reality?**
2) Whether or not these laws of physics are deterministic.
3) Depending on the answer to (2) – what does that say about predicting human behavior.
If the answer to (2) is yes; that we live in a clockwork type universe, then the answer to (3) is, surprisingly, not really! Even if a computer with infinite precision, we would still need perfect accuracy. So in practicality no.
But the answer to (2) turned out to actually be no. That is, as we currently understand it, there is genuine randomness baked into the fundamental laws of the universe. There is therefore no possibility of prediction.
**On a certain level this is imprecise: if you allow for the existence of things like God, a soul, or whatever; i.e. things which aren’t bound by the “laws of physics” – that is nonsensical because they still exist – so they are still “natural” – and they would still obey some laws. Nonetheless, it’s not immediately clear that you couldn’t describe a “natural world” which obeys laws of physics and a “supernatural world” which can intervene in the natural world but doesn’t obey any physical laws….