Plus: What steps to take if someone's snooping through your phone.

Photo: Getty Images

Pop quiz: You're hanging out on a lazy Saturday and your boyfriend leaves the room. While he's gone, his phone lights up with a notification. You notice it's from his hot coworker. Do you A) Decide it's none of your business and look away, B) Make a mental note to ask him about it, C) Pick it up, swipe in his passcode and read it, or D) Use it as permission to go full Mr. Robot and go through his phone top to bottom? Choosing the first option requires the self-control of a saint-the temptation to snoop in someone else's phone is so real. But if you choose anything but option A, you might be on shaky legal ground. It turns out that going through your partner's digital information could get you in hot water with the law if he or she got mad enough about it to go to the police-not to mention what it says about having trust in your SO.

It may sound scary, but understanding these ins and outs is more important now than ever, considering just how many people are engaging in some form of tech snooping. "Depending on which survey results you read, anywhere from 25 to 40 percent of people in relationships admit that they have secretly checked their significant other's e-mail, browser history, text messages, or social media accounts," according to Judges Dana and Keith Cutler, real-life attorneys (and married couple) practicing in Missouri and presiding judges of the just-premiered show, Couples Court with the Cutlers. "The technology to follow up on that 'gut feeling' of suspicious activity is available, and people are using it."

Before you spy (even just for a second!), here's what you need to know:

It all comes down to three issues: ownership, permission, and expectation of privacy. The first rule is pretty simple: If you don't own the phone, you're not allowed to do anything without the other person's permission. But "permission" is where things get murky. Ideally, your boyfriend would give you his passcode and say you're allowed to look at anything you want anytime you feel like it, and you would do the same, because you trust each other completely and are obviously too pure for this world. But that's not usually real life (and if it were the case you probably wouldn't need to snoop in the first place). So if he doesn't give you his passcode, then you need to get permission on an ongoing basis.

"Permission is a tricky concept because it can be limited or revoked," Judge Dana Cutler says. "Just because a particular emergency once required him to tell you his password does not give you a perpetual license to go snooping through his phone looking for pictures and texts anytime you feel like it." Not to mention this isn't super-healthy behavior in the first place. If you feel like your only resort is to sneak into your partner's phone, then you might need to rethink your relationship-or at least look into couples' counseling.

Under U.S. law, people have a right to an expectation of privacy, even with close loved ones, Judge Keith Cutler explains. This means that if he hands you his phone and shows you something or leaves his screen unlocked and open where you can obviously see it, he is not expecting it to stay private. Other than that, you have to ask first. It can be frustrating to be with someone who will share a toothbrush with you but not their phone, but ultimately that's their call to make. (And it's your call to decide if this is something you can live with in a relationship.)

Things go from murky to straight-up illegal if you guess his passcode, figure it out from watching him, or "hack" it a different way. "If he's not aware that you know his password, and you have to unlock and open a series of apps on his phone while he's asleep to find what you're looking for, you've probably crossed the line at that point and have wrongfully invaded his privacy," Judge Dana Cutler says.

Thankfully for curious (or suspicious) partners, there are other forms of snooping that are kosher. Social media, for instance, is fine. If he posts something publicly, you're well within your rights to go through it with a fine-tooth comb. It's also legal to "backdoor" information, meaning that you go through public postings of mutual friends to see things your partner might be commenting on or liking. You can't, however, read his private messages, Judge Keith Cutler adds.

But what if you're the one who is in the position of having your lover snooping through your phone? If you didn't give him your passcode or otherwise grant permission and you didn't leave it lying around unlocked and the screen on, then it's a legit issue. Reduce anyone's temptation to take a casual glance by making sure you're already taking basic privacy measures, Judge Keith Cutler says. Change your passcode and passwords and remove notifications from your lock screen.

If it goes further than inappropriate curiosity, it may cross the line into digital stalking. Protect yourself immediately by setting your social media settings to private and unfriending mutual friends. Make sure you close out of apps and lock your phone screen every time, and contact your phone company about setting up additional security on your line. Your last resort, in extreme cases, is to call the police and file a criminal complaint. While it's unlikely that law enforcement will get involved in a simple "he read my texts!" case, if there is a threat of violence or bodily harm, if it's part of a pattern of stalking, or if your info has been used for fraud (identity theft) then they'll take it very seriously, Judge Dana Cutler says.

Bottom line: Don't snoop into other people's phones, no matter how tempting it is. If it's happening in your relationship, then it's time to have serious thoughts about if you really want to be with someone you don't trust. At best, this type of behavior (by you or your partner) is not healthy. And at worst, "digital abuse" can be part of a larger pattern of, or precursor to, domestic violence.