Old Mr.Rakesh was found dead in his bedroom by young Manish.
Manish recounted his dismal discovery to Detective FBI detecive Donald, who happens to be around the scene.

'I was walking by Mr. Rakesh'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.'

With clue from Detective FBI detecive Donald, the police officer immediately arrested Manish for the murder of Mr. Rakesh. How did he know Manish was lying?

FBI Detective Puzzle

Frost forms on the inside of the window, not the outside. So Manish could not have wiped it off to discover Mr.Rakesh's body.