A state judge sentenced 19-year-old Michael Robles to 20 years in prison Wednesday for manslaughter for fatally beating a taxi driver in Waipahu last year.

Robles is the first of two teenagers to be tried for the killing of Charlys Ty Tang on May 1, 2010, Tang’s 41st birthday.

Eighteen-year-old Kilani Derego is scheduled to stand trial for murder in February.

Robles was also charged with murder. But Circuit Judge Dexter Del Rosario in June found Robles guilty of manslaughter because, he said, the state did not prove Robles intended to kill, or knew his actions would lead to Tang’s death.

Robles on Wednesday apologized for what he did to the mother of Tang’s children and offered her his life in return.

"It there is anything that I can do in return, I give you my 100 percent mind, body and soul to do it," he said.

None of Tang’s family members attended Robles’ sentencing.

Prosecutor Scott Bell rejected Robles’ offer on their behalf.

"Mr. Robles does not have anything that Mrs. Tang wants. Indeed, there is nothing that Mr. Robles could give, offer or say that could make right what he did," Bell said.

William Jameson, Robles’ lawyer, asked Del Rosario to sentence his client to eight years in prison under a state sentencing law that reduces the penalties for adult defendants who have not yet turned 22 years old.

Del Rosario said Robles deserves the maximum penalty for manslaughter, in part because he believes Robles minimized his role in the beating when he testified in his trial that he kicked Tang only to get him to release Derego.

At the time of the beating Robles and Derego were residents of a Hale Kipa group home in Manoa for at-risk teenagers.

Robles is the only person so far to provide an account of the beating.

In court papers Derego claims he was not even there.