I'm certain its Charles Grodin, and there a crime, a murder and/or theft, and Charles Grodin's character passes the investigation's interrogation, including a polygraph test. And it's the big surprise twist at the end that Charles Grodin has a twin and he did it. It seemed like a very low production film.

I think it must have been before he did The Great Muppet Caper, cause it seems to have some light cross over similarities.

At the link below, there is the filmography of Charles Grodin from 2006 to 1964,
With a plot summary for each one. The only one not listed is "The Ex," from 2007.
None of the plots match your description. Is it possible that it was another actor?

Charles Grodin Filmography