Witch Doctor was another unfamiliar term to Leon. He had no idea what a Witch Doctor can do, but he assumed anything with a doctor in its name had to have something to do with treating people.
"This is… hypnotism, isn't it?" Leon asked.
"Interesting, so you can also understand this much with a glance. That is right. Master Woodrow is using hypnotism to stop my son from rampaging." The Old Shaman explained with an approving nod. If the person could not even see this much, he would begin to doubt his judgment.
The reason he decided to trust Leon despite the person having nothing to prove he was a skilled doctor or a doctor at all for that matter, was not because the Old Shaman was crazy.
It was because the Old Shaman had sensed a particular wavelength from Leon that only Shamans possess and decided to wager on that small possibility that Leon could do it.