A prosecutor is part of an institution for years that, by default, it's reasonable to assume has some culpability for the crime. Someone caught by an undercove

A prosecutor is part of an institution for years that, by default, it's reasonable to assume has some culpability for the crime. Someone caught by an undercover cop is interacting with that cop for the first time. For this reason, by default, the cop is not assumed to have culpability.