An academic has asked a court in the US to order a death certificate for Billy the Kid to settle questions about whether the infamous outlaw was actually killed in 1881.

A death certificate would end tales that the Kid was not fatally shot by Lincoln County sheriff Pat Garrett, said Robert J Stahl, a professor emeritus at Arizona State University.

Some claim Garrett shot someone else, and Billy the Kid took up ranching and farming or escaped to Texas, living under an assumed name.

It is reported that Mr Stahl filed a petition in the state district court in New Mexico.

He had gone to the state office that registers births and deaths and was told he would need a court order for a death certificate to be issued.