If you are looking for it or asking this, you probably know in your heart it is going on. I caught my husband because the way he was acting was just not right so I reviewed his cell phone bill. Not a pretty sight. Or, you could just ask her - if she's doing it she just might tell you.
Prove opportunity, inclination and intent. There must be evidence of some relation between the parties and such conduct on their part as would tend to establish that the desire and willingness existed to engage in an act of adultery when the opportunity arose.
Proof of opportunity to commit adultery, alone, is insufficient. The evidence of inclination and intent must be clear, positive and satisfactory, such as to lead a reasonable person to the conclusion that the adulterous act was committed when the opportunity was present. Where it is shown that the parties charged with adultery had the lascivious desire and the opportunity to gratify it, the fact that they gratified it may be inferred from other facts.
-------------------- Never let your sense of morals get in the way of doing what's right. Isaac Asimov