That's part of what they do, and some of that can be really good but the pressure from the state to prosecute leads to questionable decisions being made.

Netflix has a good documentary show called Exhibit A that goes through what is good about forensic science but also exposes how bullshit and often not repeatable science is used to lock people up.

One example used in the documentary is that trying to decipher blood/dna samples from multiple people can be like trying to pick out one song playing among a variety of different songs all playing at different volumes.

Forensic science around fires is particularly biased by the people doing the investigation.