Washington (CNN) -- Drones both dazzled and worried senators at a hearing Wednesday about their use within the United States, and lawmakers and experts said that new legislation may be needed to protect the privacy and safety of citizens.
Judiciary Committee Chairman Patrick Leahy, D-Vermont, held and studied a small plane weighing just 2 pounds before beginning the hearing.
"I am convinced that the domestic use of drones to conduct surveillance and collect other information will have a broad and significant impact on the everyday lives of millions of Americans," said Leahy.
Sen. Charles Grassley of Iowa, the ranking Republican on the panel, said the technology may require lawmakers to develop a new definition of an unreasonable search, which is banned under the Constitution's Fourth Amendment.
"The thought of government drones buzzing overhead monitoring the activities of law-abiding citizens runs contrary to the notion of what it means to live in a free society," Grassley said. The small aircraft can be fitted with lightweight cameras.
Amie Stepanovich, of the Electronic Privacy Information Center, said law enforcement should not use drones as an alternative to police patrols. She said that they should be used for specific operations and that Congress should pass a law requiring legal permission.
"I think we do need to enforce a warrant requirement for drones in circumstances where they're collecting criminal evidence," Stepanovich said. She said exceptions could be made for emergencies.
"With the ease and availability of drones, I think there is a real concern that the day-to-day conduct of American citizens going about their business might be monitored, catalogued and recorded by the federal government," said Sen. Ted Cruz, R-Texas.
Privacy laws need to be updated to account for drones and other new technologies, according to Ryan Calo, of the University of Washington Law School.
"There's very little in American privacy law that would limit the domestic use of drones for surveillance," Calo said. Calo said he thinks the aircraft can be extremely beneficial but warned that Americans may oppose their use unless there are some limits.
An industry representative said the federal government already is regulating unmanned aircraft systems, the name industry uses for the aircraft.
"The (Federal Aviation Administration) strictly regulates who, where, when and why unmanned aircraft will be flown," said Michael Toscano, president and CEO of the Association for Unmanned Vehicle Systems International. He said operators of planes must get a certificate of authorization from the FAA, and the craft are to be flown under 400 feet and primarily in daytime hours.
The FAA is supposed to allow widespread use of domestic drones in 2015. There is only limited use by civilians at present. Because they are cheaper to use than helicopters, unmanned aircraft can be used to monitor crops and livestock, look at damage to buildings and for other uses. The FAA recently announced plans to create six drone test sites around the country.
The Mesa County Sheriff''s Office in Colorado already uses drones. Benjamin Miller said the craft can help find missing people and photograph crime scenes. Miller noted it's not legal to arm domestic drones.
"It may well not be legal to carry any munitions on a drone," said Senator Dianne Feinstein, D-California. "But what can be done illegally, and how can the government prevent that from happening?"
Sen. Amy Klobuchar, D-Minnesota, expressed concern that as drones are more commonly used, they could be involved in accidents. "What would happen if one of them hit a small plane?" asked Klobuchar. "Like when birds hit a plane, it can create problems."
Toscano replied, "If there were a collision, then there could be damage."