Planning Your Entrance
There are a few ways to get in.
The big decision you'll have to make is what level of challenge you want to have. There's an easy way and two needlessly difficult ways (at least two).
Charm: The easy way, is to just walk right in the front door. Save and then talk to Haas at the front desk. It seems that he was with you for the infamous Mexicantown shooting, so you go back a fair bit. Your goal is to sweet talk him into letting you have access to the restricted area.
There appear to be a few ways to do this. I managed it with nothing but absolve. If your combination doesn't work, just revert to the old save and try again. Heavy absolution works quite well though, so stick to it if you can. He should agree to give you temporary permission, which will at least keep the officers from shooting you on sight, which is nice. Even if you just plan to aggressively snoop, you're at a big advantage if they're friendly to you.
Sneak In: If you don't care about this advantage, there are a few back routes into the station. If you get to the rear alley, you can either get in through the sewer or the fire escape. To get here, you either have to have augmented legs and leap over the fence by using the dumpster or go through the side alley. The alley's on the map, but it is also electrified at the moment.
If have a skin augmentation that gives you a defense against electricity, then you can just wade through it. Otherwise, grab the box inside and drop it into the water, then walk back out and leap over the barricade by the punks. You can grab another large crate here. With these two crates, you can make a little bridge and slowly make your way down the hall. Leap onto the dry spot around the corner, and then flip the breaker to make it safe. You should also be able to go down the manhole across the street from the police station to reach it, but you'll need to watch out for some armed thugs in the tunnels.
Once you're in the back alley, you can either go down the manhole (or stay in the sewer) and then stick to the left side to climb up and find the back entrance to the morgue with a level 3 lock. If you can kill the laser field with a level 2 hack, then you can easily slip in, stun the single guard watching the entrance, dodge the camera's view and enter the morgue.
The other entrance to the police station is the fire escape, which takes you up to a vent at the top.