The key answer of exercise 6

Mr Smith's house was broken into by a 20-year-old student last Wednesday. £1,000 and two rings were stolen. He escaped without being seen by anyone. He was arrested by the police two hours later. He was charged with burglary. He will be tried by a jury next week. He might be sent to prison for up to ten years. How was he found by the police? Well, the Smith's computer was used to check his Facebook account, but he forgot to log out before he left.