The Lord Mansfield Doctrine

There's this doctrine called the Lord Mansfield Doctrine. It's from the early 1800s and it's based on Old English common law. He is presumed to be the father of every child that his wife has while he's married to her. So even if he is deployed in active combat duty while he's still married to her, everyone knows she's living with the boyfriend. The judge says, according to the law, you are responsible for any children she has while you're still marriage to her.