And I understand the need to keep up appearances, but I didn't necessarily think it was a good idea for Grover to involve his wife by having her take Clay's phone and then leave her alone with him. If he killed his own wife, what's to stop him from killing Grover's wife to cover-up his wife's murder?
Yeah, that bothered me as well.
If you suspect your cop friend murdered his wife, get her the hell out of the house. What if he somehow catches wind that you're investigating him and takes her hostage? Grover repeatedly made the point about how good his former partner was at reading people.
Then, to make matters worse, he tells his wife what he suspects and leaves her in the house with the guy, where it's entirely possible she could reveal their suspicions to him with her body language, verbal responses, and nervousness.
Then, worse than that, Grover sends her on a damn mission to steal the alleged murderer's phone.
Then, worst of all, he leaves her in the house with him for hours while the phone is mission so the guy can angrily confront her about it.
What the hell, Grover? Take some time to make sure your wife is in a safe place before going to work and steal the phone yourself when you get a chance. They'll wait for you. And if the partner woke up and found her missing, he might just assume she left to go do something.