Prosecutors on Friday demanded life imprisonment for a former U.S. civilian base worker charged with raping and killing a 20-year-old woman in Okinawa in April last year.

Claiming Kenneth Franklin Shinzato, 33, committed "extremely heinous and selfish crimes," the prosecutors sought the life term, while the defendant denied intent to murder the victim. The Naha District Court will hand down a ruling on Dec. 1.

The case sparked public anger and strengthened anti-U.S. base sentiment in Okinawa, which hosts the bulk of U.S. military facilities and has seen a series of crimes committed by U.S. servicemen or military-linked personnel.

According to the indictment, Shinzato attacked the woman for the purpose of raping her on a road in Uruma in central Okinawa around 10 p.m. on April 28, 2016. He stabbed her in the neck with a knife and struck her on the head with a bar so she would not resist, killing her as a result.(Supplied Image)

The remains of the woman, who was taking a walk at the time of the crime, were found on May 19 of that year in a wooded area in the village of Onna, north of Uruma. They were found based on information in Shinzato's statement. The accused has admitted to the charges of rape resulting in death and abandoning the victim's body.

In their closing arguments, the prosecutors maintained Shinzato "stabbed the victim in the neck with a knife three to four times and struck her with a bar on the back of her head five to 10 times, therefore he had intent to kill the victim."

They also said Shinzato committed "grave" crimes as he "assaulted an innocent woman like a phantom killer and took her future."

"No sincere apologies have been offered to the victim's family and he has shown no remorse," the prosecutors said, adding he had premeditated the crimes by preparing a knife and a suitcase to transport her body beforehand.

They said they had thought about seeking the death sentence but "reluctantly gave up the idea in light of striking a balance (of punishment) with other similar criminal cases."

Ex-U.S. base worker denies intent to kill Okinawa woman

The accused said in his last statement during the trial, "I did not intend to cause such a result." The defense counsel also requested that the court "forget about (local residents') frustration with U.S. bases" when deciding on the ruling.

Shinzato's defense counsel repeated his denial of murderous intent and said there is a possibility that the woman died as a result of falling and hitting her head on the ground.

The defendant was working at an internet company within the premises of the U.S. Kadena Air Base in Okinawa at the time of the incident after serving as a U.S. Marine from 2007 to 2014, according to his lawyers and the U.S. Defense Department.

While the southern Japanese island prefecture has been following the trial of Shinzato, which began last week, a 21-year-old U.S. Marine was arrested on Sunday over an alleged drunk-driving accident that killed a local resident in Naha.

On the following day, the U.S. Forces in Japan prohibited all U.S. service members from drinking alcohol on or off base.