Which principle could be used to date a stack of horizontal rock layers?

In a property settlement after a divorce, the wife was awarded all personal property that had been accumulated during the marriage, including the husband's classic 19-inch black-and-white tv set. in order to get his prized tv set back, the husband lied to his friend, telling him that the wife took the tv set in violation of the property settlement. the friend remembered that the wife gave the friend's wife a key to her new home, and he volunteered to go with the husband to get the tv back while the wife was at work. the husband and the friend went to the wife's house, but, unbeknownst to them, the wife had taken the day off work. after the friend noisily opened the back door with his wife's key, the wife called the police, who quickly arrived and arrested the husband and the friend. as to a charge of common law conspiracy to commit larceny, how should the friend be found?