Dr. Rolando Ortiz II, of the James Gordon Memorial Hospital in Olongapo city, west of Manila, told the court he examined the 22-year-old woman — identified by the court only as "Nicole" — two days after she was allegedly raped by a Marine while the three others cheered him on.
Asked if her injuries were consistent with rape, he replied, "It is consistent."
He said the woman suffered bruises on her arms, legs and genital area.
The rape charge is punishable by up to 40 years in prison. The Marines have refused to answer the charge, and the judge entered a plea of innocent for them.
Prosecutors contend the woman was attacked Nov. 1 in a van at Subic Bay, near Olongapo, by Lance Cpl. Daniel Smith as Lance Cpl. Keith Silkwood, Lance Cpl. Dominic Duplantis and Staff Sgt. Chad Carpentier cheered on the assault.
The Marines had just finished counterterrorism maneuvers with Philippine troops.
The case sparked anti-American protests in the former U.S. colony and is seen as a black mark on exercises credited with helping weaken Al Qaeda-linked militants in the country's restive south.
The men were part of the 31st Marine Expeditionary Force stationed in Okinawa, Japan.
The U.S. Embassy, which has custody of the men under a treaty with the Philippine government, hasn't released their ages or hometowns.
During cross-examination by defense lawyers, Ortiz said the bruises could have been 12 hours to four days old, so they could have been sustained before the alleged rape.
They also could have been caused by activities other than rape, Ortiz said.
Jose Justiniano, a lawyer for Silkwood, said Ortiz's statement did not conclusively show that the bruises were caused by the alleged rape. Evalyn Ursua, the woman's lawyer, said the medical findings must be seen in relation to other evidence, which all together support the allegation.