Here’s one cop show cliche that’s actually true IRL.
If you are being questioned by the police, it is a felony (possibly several) for YOU to lie to them about ANYTHING (including by omission), but with a few minor exceptions, THEY can lie to you about almost EVERYTHING.
It doesn’t matter if you’re a suspect, a victim, a material witness, an innocent bystander, or anything else.
It doesn’t matter if you’re at the police station, your own residence or workplace, the crime scene, or anywhere else.
That’s probably another cop show cliche that’s actually true IRL-- if the police say to the press, or whomever, that someone they questioned is just a “person of interest”, everybody knows that’s just a cute euphemism for “number 1 suspect”.
While it’s certainly true that lying to a federal agent is against federal law that’s often not the case at a local level. I got lied to all the time. There were a very few things that could get you arrested. Giving a fake name when stopped for a violation. Pretending to be someone else to keep from getting arrested on a warrant. Mostly things that would hinder your apprehension. Telling me you were at the movies when you weren’t? Not illegal. I can’t say that’s true of all states but it’s 100% correct for mine.
Even with the feds a lie has to be about material information concerning a crime. You can go full Joe Isuzu if you want and it’s not a crime unless the lie is related to a crime under investigation.
We are getting in danger of taking a fun CS topic and turning it into FQ. There are very few lies a cop can say that would be illegal. It’s not a crime. But every state will have its own caselaw that will define what can be said. I worked under a set of caselaw that was much different than another state would be. It wasn’t a free for all. There were boundaries that couldn’t be crossed. I wouldn’t get arrested or lose my job if I made a mistake and crossed one of those boundaries but the interview would be tossed, everyone’s time would be wasted and the case might be ruined.
But if there’s one thing I’ve learned from cop shows, it’s that if you do want to smack the suspect around a bit, all you need to do is reach up and unplug the camera in the corner. Noone will think that an eighteen-minute gap in the videorecording that ends with a bruised suspect shakily signing a full confession is in anyway suspicious.