Do you swear to tell the whole truth and nothing but the truth? Raise your right hand please. Why? Because the court needs to see if you have a brand burned onto your hand.
Centuries ago keeping records of previous offences wasn't as easy as it is today so someone devised a simple plan. A brand on the inside of the hand. Then, when in court, it was easy to tell if the person on trial had a previous conviction when they raised their right hand.
They had a permanent record.
You would think a hot iron applied to skin would discourage people from being repeat offenders—but perhaps not so much.
Elizabeth Brown, when imprisoned, had been twice branded on the cheek and once on the hand. She often broke two Commandments at once: Thou shalt not steal and Remember the Sabbath Day to keep it holy. She tended to pick pockets at church.
For more about Elizabeth Brown, scroll down to the 15th criminal at:
http://www.oldbaileyonline.org/browse.jsp?id=OA17170320&div=OA17170320&terms=sweetbones#highlight
For a more in-depth look at the origin of raising the right hand:
http://nwsidebar.wsba.org/2013/10/21/raise-right-hand-court/
I wish Elizabeth Brown was a fictional character because her story is tragic in many ways. But someday I might write about a lady who picks pockets in church...