One spouse’s fear that the other is not being faithful is — and has always been — the central motivation for spousal spying. The big difference now compared to even a year or two ago is in the tools available to check out that suspicion.

Just consider the following: GPS trackers so small they can be placed easily into children’s toys or an article of clothing; matchbox-sized cameras; software that copies messages and sent emails; and spying software that can be installed on another party’s cell phone.

Legally, can spouses do that to each other? Is evidence gathered in such a way admissible in a divorce, child custody, property division or other family law case?

The answer is clear only for its uncertainty: Jurisdictions are split, with an identical case being potentially resolved a certain way in one instance and another way in another.

At bottom, courts are often concerned with a person’s reasonable expectation of privacy. Sometimes there is a problem with getting judicial arms around that it in a case even not involving married parties. Within marriage, understanding precisely what privacy should mean can be far more complex.

For example, courts in certain states have ruled a violation of privacy rights in cases involving secret recordings and camera installations. In a recent case from Minnesota, a man who installed software on his wife’s computer and car was convicted of stalking and jailed.

Conversely, two U.S. circuit courts have ruled that secretly recording a spouse is not prohibited by law.

Regardless of court rulings, it is clear from rising gadgetry sales and the statements of many family attorneys, investigators and spouses themselves that marital spying is on the rise and growing dramatically.

“You can have all the laws you want,” says one ABA principal, “but I think this is going to go on.”

Source: The Wall Street Journal, “A spy-gear arms race transforms modern divorce,” Steve Eder and Jennifer Valentino-Devries, Oct. 5, 2012