Here’s how to discern the truth by observing changes in behavior, social patterns, and other non-invasive methods.

Pay attention to any significant changes in your partner's behavior. This might include unusual secrecy, sudden over-protectiveness of their personal devices, changes in intimacy, or unexplained absences. These shifts could be indicative of something amiss.

Sometimes, mutual friends may notice changes or odd behavior that they may share, consciously or unconsciously. While it’s not advisable to involve too many people or start gossip, a casual conversation with a trusted mutual friend might provide some insights.

Look for anomalies in how they use social media. A sudden increase in activity, new privacy settings, or unusual interactions could hint at something. Remember, this doesn’t involve breaking into their accounts but merely observing from a distance.

Instead of snooping, openly ask to use their phone for a legitimate reason, like making a call or checking an address. Watch their reaction closely; if they become noticeably nervous or defensive, it might warrant a deeper conversation about trust.

If you have legitimate access to shared financial accounts, you might notice unusual transactions that don’t add up. Large, unexplained withdrawals or payments to unknown entities could be a red flag.

Physical receipts in wallets, bags, or car compartments can tell you a lot about where they’ve been, especially if the places and expenses are unusual or unexplained. Are they buying items you've never seen or paying for things you don't know about? This could be a sign.

Dropping by their workplace or home unexpectedly (within reason and without violating privacy) can reveal a lot about their routine. If their reaction is overly negative, you may need to discuss why.

Keep an ear out for details in their stories that don’t make sense or keep changing when retold. Inconsistencies could indicate they are fabricating or altering details.

When confronted with questions, some might use anger or resentment as a shield. If your partner consistently turns defensive or tries to start an argument to avoid discussing certain topics, it might be a tactic to deter scrutiny.

The most effective way, though perhaps the hardest, is to have an open and honest conversation about your feelings and fears. Express your concerns without accusing and see how they respond; often, communication can solve many misunderstandings.

In investigating a cheating partner, it's important to remain respectful and avoid violating their privacy. These steps are about observing and communicating rather than accusing.

If your suspicions persist, professional counseling might be a helpful next step for both parties, regardless of the outcome.

Trust is a critical component of any relationship, and addressing these issues forthrightly is crucial to maintaining a healthy partnership.