What's the status on the use of a lie detector relating to a cash loss from a dual custody environment? Is that option legal at this time?

Are there other investigation methods to consider?

Some States permit it, some don't. Of those that do, most require that you inform staff in your handbook that they may be subjected to a lie detector test.

In other words, call your attorney.

There's also a federal polygraph protection act that applies to employees- it should be posted on your premises along with things like FMLA, child labor, minimum wage info...