Truth doesn't matter. If you "get the charges through", you're successful, with little to no penalty for failure, as a LEO or prosecutor. Innocence and guilt are irrelevant. Justice, fair punishment, and rehabilitation are also not relevant. Success is measured by man-years in prison (or arrests for law enforcement). Usually there's room to just blame someone else if you do face scrutiny. Honestly, I think this is a result of greater cultural issue in the US (maybe other countries too, I just can't speak for the culture).