WASHINGTON — Targeted killings have made drones controversial, but a new class of tiny aircraft in the United States — cheap, able and ubiquitous — could engage in targeted snooping that existing laws are inadequate to address, witnesses and members of the Senate Judiciary Committee said in a hearing on Wednesday.

The drones, or unmanned aerial systems, have already helped the police find missing people and county planners measure the growth of a landfill. But they could also be used by drug dealers, pedophiles and nosy neighbors, the witnesses and a senator said.

Surveillance by government is limited by the Fourth Amendment’s protection against unreasonable searches and seizures, and snooping by corporations and individuals is covered by privacy law and common law. But these were not written with drones in mind. The issue has taken on new urgency as the Federal Aviation Administration prepares to set forth rules for drones’ commercial use and as prices for the aircraft drop. Many states are considering legislation, but Congress is only beginning to consider the problem.

“There’s very little in American privacy law that would limit the use of drones for surveillance,” said one witness, Ryan Calo, an assistant professor at the University of Washington School of Law. “Drones drive down the cost of surveillance considerably. We worry that the incidence of surveillance will go up.”