Riddle: Old Mr. Tilly was found dead in his study by Mr. Foster. Mr. Foster recounted his dismal discovery to the police. "I was walking by Mr. Tilly`s house when I thought I would just pop in for a visit. I noticed his study light was on and I decided to peek in from the outside to see if he was in there. There was frost on the window, so I had to wipe it away to see inside. That is when I saw his body. So I kicked in the front door to confirm my suspicions of foul play. I called the police immediately afterward." The officer immediately arrested Mr. Foster for the murder of Mr. Tilly. How did he know Mr. Foster was lying?
Answer: Frost forms on the inside of the window, not the outside. So Mr. Foster could not have wiped it off to discover Mr. Tilly`s body.