The first of two teenagers to stand trial for the beating death last year of taxicab driver Charlys Ty Tang was sentenced this morning to 20 years in prison for manslaughter.

Michael Robles’ lawyer was hoping his 19-year-old client would receive a sentence of eight years in prison under a state sentencing law intended for adult defendants younger than 22.

The other teenager, 18-year-old Kilani DeRego, is scheduled to stand trial for murder in February.

Tang, a native of Cambodia, was fatally beaten on his 41st birthday after he picked up two passengers in Waikiki about 1:15 a.m. on May 1, 2010. He drove them to the Times Super Market in Waipahu, where he was found severely beaten at 1:50 a.m. He died that day.

Tang lived in Waikiki with his wife, Xiao-Ling Tang, and their two children.

Robles had been charged with murder but Circuit Judge Dexter Del Rosario, in a non-jury trial, convicted Robles of manslaughter on June 2, 2011. During the trial Robles testified that it was DeRego who had beaten the driver, and the judge ruled that the prosecution did not present sufficient evidence to support a murder verdict.