Capcom's Resident Evil 3 remake contains major and minor changes from the original RE3 released in 1999. Several of those can be found in the Raccoon Police Department (RPD), but you'll need to know where to find the S.T.A.R.S. ID card to access (and benefit from) them.
Before we dig in, take note that this guide contains SPOILERS for the plot of the Resident Evil 3 remake, and reveals the fate of the Resident Evil franchise's most enduring characters.
Where to find the S.T.A.R.S. ID card
Approximately halfway through the game, you will take control of Carlos for a brief sojourn through the RPD. In the courtyard out front of the station, Ty, Carlos's partner, works frantically to break into the RPD, leaving Carlos to deal with a zombie wandering near the entrance. Long-time fans should recognize that zombie as Brad "Chickenheart" Vickers.
You have two options. Avoid Brad until Ty gets the doors open, or gun him down. Avoiding Brad is the easier option, but letting him live (if he can be thought of as alive) deprives you of an Achievement/Trophy, as well as the S.T.A.R.S. ID card.
Brad drops the S.T.A.R.S. ID card when he dies, so you will need to harden your heart and rip into him with Carlos's pistol or assault rifle. Brad's got quite a bit of health, so the assault rifle is the most efficient option, not to mention the safest. Don't worry about burning ammo on Brad: There's plenty to go around inside. When Brad meets his end, the S.T.A.R.S. ID card drops near his body. (Killing Brad for the first time will also unlock an Achievement/Trophy.)
You will need the ID card to open several of the strongboxes scattered around the RPD's interior as part of the Master of Unlocking Acheivement. They don't have to be opened, but overlooking them, or if you don't have the S.T.A.R.S. ID card to open them, will cause you to miss out on ammo and other goodies. Fortunately, the cases are hard to miss: Any rooms colored red on your map contain either an item you neglected to pick up, or a case that can be unlocked using the ID card.
Once you know where to find the S.T.A.R.S. ID card, check out our Resident Evil 3 guide for more pro strats such as how to instantly load grenades in Jill's grenade launcher, as well as walkthroughs for the game.