Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

This is the property invoice of Jack Ruby's belongings, the things that were taken from him.

And it includes:

They weren't just making note that he was wearing a set of underwear. They were noting the things they took from him. 

And if you are going to argue that they didn't take the underwear, then it means that he was wearing his own underwear, including his own socks:

And those sock are obviously not these socks: