I got pulled over for being lost in the wrong neighborhood. I was relieved as I did not have a GPS at the time, horribly lost was hoping the cop that had been tailing me for the last mile would pull me over to get directions. He wants to know why a kid like me is in a neighborhood like this. I explain I'm lost. He doesn't believe me says I'm here to purchase something illegal. My whole attitude changed because I'm suddenly nervous. Why would he think that and realizing this could go badly. He says only guilty people act nervous. He ends up calling a K9 unit to search my car. The other cop is really cool. We chat and he apologized for first cop being a jerk. After the search he gives me directions on how to get to my destination.
Good cop/bad cop is real.
I knew a police helicopter pilot and I asked a similar question when searching for suspects. He said that the bad guys were the ones NOT looking up at the helicopter. Innocent people look, point, stare, etc.
I'm one of those jumpy people. I've been pulled over and screamed at, "Why are you so nervous?! What are you hiding?!" And another time, the cop was very nice and just said, "Relax, it's just a ticket, are you okay? Do you want to catch your breath, not a big deal, take a couple deep breaths, buddy," super friendly and helped me relax. I get anxiety in those situations without any real cause, I just get really nervous.. It's crazy how differently cops can handle the situation in the exact same circumstances just one was nicer (or trained better).
Cop here, I'll give a serious answer instead of all the others.
Assuming this is on a traffic stop, for the most part, if you are acting jumpy I try to figure out why and remove that stress. If I can't figure it out on my own, I'll just simply ask.
Common answers are: "I don't like cops" "I don't want a ticket" and so on.
My reasoning for this is if you're relaxed and I ask if there are any weapons in the car and your stress indicators skyrocket when you say no, something is wrong. If you're already stressed, I won't be able to see that reaction.
As others have stated, it's not 100%, some people are just nervous nellies. I try to calm people down for their sanity and my safety but it doesn't always work.
I'm a Florida native and am usually dressed in shorts and a t-shirt. I was in a flyover state for a concert and was supposed to pick someone up about 4 hours away in the morning. Instead of getting a hotel for 5 hours I decided to drive to my destination and sleep in the back of the rental car.
Usually when I do this, I roll the windows down and sleep with the car off, but it was in the mid 30's this night. I pulled into a vacant parking lot next to a vacant building outside of town (turns out I was still in city limits). I tried to turn the running lights off, but wasn't able to. This eventually attracted the attention of the local law enforcement.
I woke to a flashlight banging on my window. They (all 9 of them) wanted me out of the car while they tried to figure out what was going on. Being as it was cold, I started to shake. I shared how I thought it was amusing that I was shaking and that it would likely raise suspicion. The cop that was babysitting me at that moment said 'No, it's cold out'. She then let me get into the car and start it again.
I'm a police instructor here. You look for what is out of place/context. If everyone is looking at an event or certain direction and that one person is staring at you or in the completely opposite direction that's the oddball. People draw attention to themselves by behavior that is different from the environment or expected of the environment that they are in. It's how they identified the Boston bombers everyone was looking in the direction of the explosion but the brothers were staring in the opposite direction. This technique can be applied to clothing as well if it's summer and you see people wearing heavy jackets there's something odd. Somebody keeps tapping the waistline and there's no reason for him to do that like something falling off of it and there's something tucked in their waist line drugs or weapons. Now not saying that this gives you an excuse to go up and start harassing people however it it definitely lets you narrow down the focus of your attention for what is out of place
I got pulled over for speeding on Canada Day on my way up to Ottawa from Toronto.
I did the usual routine of pulling over somewhere safe, taking the registration out and putting both hands on the wheel at 10 and 2.
The cop approaches and I ask if it's ok for me to reach over and turn down the music which I forgot to do. He starts laughing and says okay. He tells me to put my hands down since I'm making him nervous. I'm like, "You're making me nervous."
Back in Toronto I don't take any chances and the cops are usually appreciative. They have never told me to relax. It's best to err on the side of caution with Toronto police. But the out of city cops are usually pretty laid back.
We had a good ol' Canadian laugh wished each other a happy Canada day and then he gave me a ticket for 115 in a 100.
There's a bit in Bryan Cranston's book where he talks about his time as a security guard. His talent was spotting about-to-be shoplifters. His advice? People come to stores because they want something specific. In and out. Watch for the lingerers.
I'm a police officer from the UK. There is no single factor. But here are a few things I'd look for:
"Police aware" is an expression we use. Like OP said, most people feel guilty and try to act normal around the police, which normally means pretending we're not there - e.g. you begin to concentrate on e.g. eating that sandwich to an almost comic extent whilst sneaking the odd look to see what we're doing. Then you have the people who stop what they're doing and watch you intently to see if you're coming for them. These are the people who are "police aware". Of course, sometimes they're just tourists hoping to take a sneaky photo of a British copper.
Mostly it's people whose appearance or manner doesn't fit in. For example, if you go to a busy taxi rank at rush hour and then just casually mooch about rather than queuing or leaving then that's an odd thing to do. If you walk into an expensive shop wearing tatty clothes and with ingrained dirt on your hands then that's an odd thing to do. If you walk into a bar, order a drink then leave it on the counter then that's odd (and probably means you're either passing counterfeit money or pick pocketing). None of these things is illegal, but they're all things that are not entirely normal and would attract the eye of an observant police officer. Don't misinterpret these examples as "looking scruffy", that's not what I mean at all. It's about not fitting in because of your context, not just a sudden bout of "I'm normal" from someone who clearly has a reason to be where they are.
Visible signs of drug use. Sometimes in the UK you'll hear the term "heroin diet" but the same would be true for meth in the US. You can spot addicts from a mile away because they have the same look and behaviours. Without wishing to tar all addicts with the same brush, hard drug addiction and acquisitive crime often go hand in hand so when I see someone who is clearly an addict I'm immediately interested in them.
Lastly, there's intelligence. A lot of what we do is guided by specific knowledge about an area. In some areas I'll be looking out for teenage kids hanging around bike racks, in others I'll be looking out for drug addicts meeting dealers, in others still I'll be looking for bag thieves amongst drinkers. Anyone who matches the sort of person who I'm on the lookout for who also looks jumpy is going to pique my interest, but 'normal people' less so.
There really is no magic answer. There is a ton of overlap between both groups and anyone who says they can consistently spot the difference is lying to you. I'd rather judge the situation based on the objective facts rather than my gut feeling.
Everyone is different, but usually the nervous people will be polite and apologetic. Suspicious people will act more agitated and annoyed.
UK veteran and ex Metropolitan Police (UK) here.
I've just found it's all down to experience when reading people. Your mentor is everything and should be a wealth of knowledge. Learn from them.
Also, the "weirdos" tend to be regulars and someone will know them and tell you all you need to know.
I don't put much consideration on someone's nervousness to the likeliness of them committing a crime. We need reasons, or probable cause to determine that.
However, someone's "jumpiness" is a tactical cue to me that they may more likely run or fight, especially if I already have probable cause of a crime occurring. Most people are scared when stopped by the police, but this fear is different than "jumpiness." Fear is a little more subdued than the tension of someone looking for an escape.
Another consideration is that if someone suffers from a mental illness, their symptoms are usually clearly different than someone who is plain scared or jumpy. Also, someone who is affected by drugs clearly has distinct signs.
It's pretty complicated to explain, but simple when observing it in person everyday.
I will say "They talk way too much"
When the customer was trying to pull something on us most would talk a lot about nothing. Keep up a constant stream of chatter. Of course this is in no way a 100% indicator, but it was one sign we looked for.
The funny thing is, if I'm off duty and around a uniformed officer I don't know (different dept, area, etc.)... I get nervous. My heart sometimes skips a beat when I see one of our own cars driving down the road, even though it may be the same exact vehicle I was assigned to just a few hours ago. My point is, I think pretty much everyone gets nervous around a cop. Most people will avoid you and not make eye contact. But what really stands out for me are the adults that will periodically look at you. Or you feel them staring at you like they're trying to ID your face. I've had to arrest a lot of people over the years, and many of them are back out on the streets.
Detective here. Take what I say with a grain of salt. I tend to deal with more serious crimes that typically are premeditated. In my experience subjects who have committed crimes are usually more calm when taking to police. They have played out the conversation in their head numerous times and know what they're going to say before you even ask them. Conversely, bystanders, witnesses, victims, etc., act more nervous when being interviewed. However, none of this is definitive. Innocent people can be calm. Guilty people can be nervous. People are individuals and need to be treated as such. In the end, I don't determine guilt, I just find facts and report them. Facts determine guilt, not demeanor.
I'm a cop in Arizona. It's important to know the cultural and societal norms of your patrol area. A huge amount of folks carry guns here for example. Your average law abiding citizen will generally use a holster, and not be deceptive about the weapon. Bad guys will not be forthcoming.