Palmer, a dentist living in the Minneapolis suburb of Eden Prairie, said in a statement that he was unaware the lion was protected, relying on local guides to ensure a legal hunt.
"I had no idea that the lion I took was a known, local favorite, was collared and part of a study until the end of the hunt. I relied on the expertise of my local professional guides to ensure a legal hunt," he said in statement through a public relations firm.
The two Zimbabwean men appeared at the Hwange magistrate's court, about 435 miles west of the capital, Harare, to face poaching charges. Defense lawyer Givemore Muvhiringi said the proceedings have been delayed by several hours because prosecutors are "making their assessments."
If convicted, the men face up to 15 years in prison in Zimbabwe.
The professional hunter who allegedly acted as Palmer's guide has been stripped of his license while he faces criminal charges, the Zimbabwe National Parks and Wildlife Authority and the Safari Operators Association said in a joint statement. The farm owner also facing charges did not have a hunting permit, the joint statement said.
Palmer has several hunts on record with the Pope and Young Club, which registers big game that archers shoot in North America, said Glenn Hisey, the club's director of records. He said he didn't have immediate access to records showing the types and number of animals killed by Palmer but noted that club records involve legal hunts "taken under our rules of fair chase."
According to U.S. court records, Palmer pleaded guilty in 2008 to making false statements to the U.S. Fish and Wildlife Service about a black bear he fatally shot in western Wisconsin. He had a permit to hunt but shot the animal outside the authorized zone in 2006, then tried to pass it off as being killed elsewhere, according to court documents. He was given one year probation and fined nearly $3,000.
Although African game isn't eligible for registration with the group, Hisey said he alerted the group's board that Palmer's ethics were being called into question. He said Palmer's domestic records could be jeopardized if he is found to have done something illegal abroad.
Cecil was being studied by an Oxford University research program.
He is believed to have been killed on July 1 in western Zimbabwe's wildlife-rich Hwange region. Trackers discovered his carcass days later.
The Associated Press