It was Annalise's idea - she guided Wes through it (and Laurel seemed to want to hide the evidence too). Connor and Michaela wanted to go to the police, and Wes and Laurel told them if they did, they'd tell the police it was Connor and Michaela who killed Sam. Based on the coin flip they should have gone to the…

I really thought it was so Philip could see that Martha really was followed (i.e. he'd notice the car/license plate matched what Hans saw)

I believe they filmed half that scene through the bedroom mirror - that's why it seems to switch back and forth.