Not quite. The prosecution fucked that up by offering him immunity in exchange for testimony. Under that agreement, Cosby never should have even seen the inside of a jail cell. They absolutely should have not made that deal, but the integrity of the justice system (if such a concept exists) demanded that Cosby be released.

If they can somehow prove that the arrest or search was illegal, that’s a huge deal and will get a ton of evidence tossed or even the whole trial nullified.