Dear Dr. Wes and Samantha: I found out my boyfriend cheated on his last girlfriend. He says that it’s because of how she treated him. Is it true that once a guy is a cheat he’s always a cheat? I want to trust him, but I don’t want to get hurt.

Samantha: I think the phrase “once a cheat, always a cheat” oversimplifies the situation. Every situation is unique, and you need more information before you make any decisions.

Tell your boyfriend you want to understand why and how he ended up cheating. You want to trust him, but you need to know more about his past. Give him a chance to state his case, but don’t take everything he says at face value. Be like an airport security worker; let the majority of his story roll past you, but stop and ask questions when things seem suspicious. Here are some key things you need to find out:

Frequency: How many times did he cheat on his previous girlfriend before they broke up? Did he cheat on other girlfriends? Did he cheat toward the end of the relationship or all the way through? If he only cheated once and then decided he needed to break up with her, his conduct, while selfish, is more forgivable than if he strung her along while cheating on her multiple times. Also find out when and where he cheated; that information may come in handy if you ever suspect he’s cheating on you.

Context: Why did he cheat? How exactly did his ex treat him? Don’t accept broad generalizations like “she hurt me” or “she said mean stuff to me.” Ask for specific examples. Remember that abuse can be both physical and emotional. While context might explain his misbehavior, it doesn’t excuse it.

Who he cheated with: Did he cheat with someone he’s still in contact with? Are they now “just friends”? If so, he might cheat on you with this person. If he has no feelings for her, then he shouldn’t be in regular contact with her.

Remorse: How does he feel about what he did? If he has learned that cheating doesn’t solve problems in a relationship and, in fact, is hurtful and dishonest, maybe he has learned something.

Most importantly, make it clear that you find cheating unacceptable. Tell him that if he’s thinking about cheating, you’d rather he just break up with you.

Wes: Well, this is a depressing topic so shortly after Valentine’s Day. Though I like her strategies, I think Samantha is more forgiving than I am. Perhaps that’s a generational thing. I see a lot of young people who seem to recover from these boundary violations more quickly than in previous generations. Or at least they think they do. I’m not so sure. It seems to go along with the whole ill-defined teen relationship problem we’ve often discussed. Or perhaps monogamy really is in its last throes in our culture.

Given what I do for a living, I spend a lot of time thinking about these kinds of things. So I have lots of little tips for the lovelorn. Here’s one befitting your situation: Don’t judge someone by how they treat the people they like. Judge them by how they treat the people they don’t like. In the young adult world, that translates into this: Never marry anyone you don’t want to be divorced from.

If your true love was a jerk to his ex-girlfriend, then he’s more likely to treat you that way, too, eventually. We like to ignore things like that at the beginning of a relationship, when everything is flowers and unicorns running through a field. But as love ages, the raw spots start to show through. Only then do you find out the true measure of your partner and the bond you’ve formed. If in the past your guy dealt with relationship problems by cheating, there’s a good chance you’ll end up on the same end of that stick when he starts to like you less.

Samantha is right. There are always complications and contexts in any relationship. However, even if he was dating the world’s worst girlfriend, she did not deserve that kind of treatment. Breaking up may be hard to do, but it beats the heck out of cheating. Guys and girls who don’t stand up and make a decision are often trying to have their proverbial cake and eat it, too. If that’s what went on with this guy, I’d suggest keeping your cake to yourself.

That said, I do believe in redemption. If as Sam notes, your guy now understands the damage cheating causes and can explain how he’s changed, then maybe things will be different. Unfortunately, young people in love tend to cling too tightly to this hopeful idea. You just want to believe that you’re so much more special than the last partner. He would never do this to you. That happened to someone else in another time and place. Maybe. Probably not.

I’ll close with my usual point for parents: Don’t expect teens to have better sexual behavior than the adults around them. If you give your child one gift in a lifetime, make it the gift of fidelity to their other parent. I could fill a book with the sad stories I’ve seen when that went awry.

Next week: The last four co-authors for Double Take join forces for the first time to reveal their inside tips for seniors headed to college next fall.

— Dr. Wes Crenshaw is a board-certified family psychologist and director of the Family Therapy Institute Midwest. Samantha Schwartz is a senior at Lawrence High School. Opinions and advice given here are not meant as a substitute for psychological evaluation or therapy services. Send your questions about adolescent issues (limited to 200 words) to doubletake@ljworld.com. All correspondence is strictly confidential.