Two cousins in the US state of Kentucky charged with attacking a gay man in a park have gone on trial.

Federal prosecutors say Anthony Ray Jenkins, 20, of Partridge, Kentucky, and David Jason Jenkins, 37, of Cumberland, Kentucky, yelled obscenities and anti-gay slurs at Kevin Pennington while trying to beat him to death in Kingdom Come State Park in Harlan County, on 4 April 2011.

The Associated Press reported on Wednesday that 20-year-old Mabel Ashley Jenkins, who has pleaded guilty to a hate crime, told jurors that the pair wanted to kill Kevin Pennington because of his sexual orientation.

Mable Jenkins is the sister of Anthony Ray Jenkins and a cousin of David Jason Jenkins.

Defence attorneys for both men acknowledged a fight took place but say Mr Pennington’s sexual orientation was not the cause and both have pleaded not guilty.

The pair face charges of kidnapping, assault and violating hate crimes laws.

Federal prosecutors say this is the first case in the US to involve a charge linked to the violation of the Matthew Shepard-James Byrd Jr. Hate Crimes Prevention Act, which was passed in 2009.

It was named after the gay Wyoming teenager who was murdered in 1998.