From: Rabbi Moshe Sofer
To: Unknown recipient
When individuals murmur that a shochet has produced treifos but refuse to testify formally before beis din, and themselves continue eating from his slaughter, their complaints amount to mere rumor. The Chasam Sofer rules leniently: without formal testimony, the shochet retains his presumption of fitness, and there is no obligation to act on such informal complaints.
Source: Shu"t Chasam Sofer YD §11