Murders are far too easy to solve. Idk if this is a setting I have, related to "game difficulty", but the longest murder case I've had is like 4 days, and 3 of those days were JUST sitting and waiting for the second murder so I could get more evidence. Do something with the murderer that decides not to leave obvious fingerprints on their left-behind business cards or crumbled up paper cipher.
In two different situations, I've gone to a crime scene, only to see the murderer shooting NPC's on his way out of the crime scene. Of course, have most murderers be less-intelligent, impulsive, etc. but I'd like to have a GOOD killer every once in a while who leaves behind no or almost no evidence. This will make the security camera and witness system a lot more important, instead of scanning every single door in a 18 story building to find the one print left on the syringe, etc.
Killers in-game have seemingly ZERO, and I mean ZERO knowledge of forensics. Nobody knows that fingerprints exist, nobody knows that it's dumb to leave the knife you stabbed someone with RIGHT next to the body. Nobody knows how to wear gloves. And too many of the killers are THRILL SEEKING. 99% of murders should NEVER contain a cryptic note, a business card, or a drawing on the wall. And the few that do should be VERY intelligent. They should have to follow much stricter rules before a kill - possibly even disabling security cameras on the floor of the apartment complex before using gloves and making sure that the victim is alone before striking.
I have only encountered TWO MURDERERS in my 40 hours of playtime that DO NOT leave behind a cryptic message. And I may have just missed it. Those two used poison, in which they then LEFT THE DAMN SYRINGE ON THE GROUND. This should not happen.
Victims should also be able to die of poison while outside of their apartment, which idk if that's already a thing.