Yechiel Michel Epstein,
Translation:Arukh ha-Shulchan…
“ Section 6 Even though an individual expert can act as judge, it is a command of the sages that he sit others with him if possible. There are those that caution that an individual should never act as a judge alone, unless he clearly states to the litigants that he is not knowledgeable enough to act as a judge and they nevertheless accept him even on the condition that his ruling is incorrect (Shach) . In truth, the populace does not seem to follow this practice, and it is known that many a Rabbi in small towns will judge alone without specifying any precondition. ”
