MANILA, Philippines >> A Philippine court entered a not guilty plea Monday for a U.S. Marine charged with murdering a transgender Filipino, allegedly after he discovered her gender when they checked into a hotel.

Marine Pfc. Joseph Scott Pemberton refused to enter a plea in the brief proceeding in a court in Olongapo city northwest of Manila, according to Justice Secretary Leila de Lima. Journalists were barred from the courtroom.

Dozens of left-wing protesters waved red flags outside the courthouse, demanding justice and an end to the U.S. military presence in the former American colony. Gay and lesbian groups have also staged protests denouncing the killing of Jennifer Laude, whose former name was Jeffrey, as a hate crime.

Monday’s arraignment paves the way for Pemberton’s trial, which lawyers of the victim’s family said is scheduled to start next month.

"Finally justice can be attained for our sibling," Marilou Laude, the victim’s sister, told reporters. She said she was shaking in anger when she saw the handcuffed suspect, who was guarded by several security escorts in the courtroom.

Pemberton has been charged by prosecutors in the Oct. 11 killing. They say the U.S. Marine strangled her and then drowned her in a hotel toilet after discovering she was a transgender woman. They had checked into the hotel after meeting in a bar.

The anti-tank missile man from Bristol, Massachusetts, was bar-hopping with fellow Marines at the time after participating in joint U.S.-Philippine military exercises.

The evidence submitted by prosecutors included statements by three Marines who were with Pemberton in Olongapo, a former liberty town when the U.S. Navy operated the vast Subic Naval Base, now a bustling commercial port.

Pemberton and some of his colleagues picked up women at the bar, checked into nearby hotels, and returned to their ship after midnight, prosecutors said. Witnesses saw Pemberton check into a hotel with Laude and then leave shortly before the discovery of her body, the prosecutors said in a statement to the court.

Marine Lance Cpl. Jairn Michael Rose, who was with Pemberton that night, said the defendant confided back at their ship that he choked the woman after discovering she was a transgender when she undressed, according to the prosecutors.

"I think I killed a he/she," Pemberton was quoted as having told Rose.

The case comes after the Philippines and the United States strengthened ties with the recent signing of a defense accord that allows greater U.S. access to Philippine military camps. The accord will help Washington’s bid to reassert its presence in Asia, and enable Manila to deter what it calls China’s aggressive moves to reinforce its claim to virtually the entire South China Sea.