In a 10-page addendum to the autopsy, released on Monday, Los Angeles County coroner’s officials said some of the bruises found on Wood’s upper body might have occurred before she drowned.
Wood was on a yacht off Catalina Island, some 30 kilometres southwest of Los Angeles, with husband Robert Wagner and fellow actor Christopher Walken over the U.S. Thanksgiving weekend in 1981 before somehow ending up in the water.
Her death was ruled to be an accidental drowning, though conflicting stories about what happened that night have since emerged.
The official explanation was that she went on deck in the middle of the night to secure a dinghy that was banging against the yacht.
Wagner wrote in a 2008 memoir that he argued with Walken that night and, later, upon going to bed, noticed that Wood and the dinghy were missing.
Her body was found a few hours later, floating in the water.
The autopsy noted bruises on both of her arms, a small scratch on her neck and abrasions described as superficial on her forehead, left brow and cheek.
The case was reopened in 2011 after the boat’s captain, Dennis Davern, said he lied to investigators at the time. Davern said Wagner also argued with Wood that night, and he blamed Wagner for her death.
"I believe Robert Wagner was with her right up until the moment she was in the water,” Davern wrote.
The report issued on Monday said the “location of the bruises, the multiplicity of the bruises, lack of head trauma, or facial bruising support bruising having occurred prior to entry in the water.”
The report was completed in June but kept confidential prior to its release.
"Since there are unanswered questions and limited additional evidence available for evaluation, it is opined by this medical examiner that the manner of death should be left as undetermined," wrote chief medical examiner Dr. Lakshmanan Sathyavagiswaran.
Wagner has not been named as a suspect. The case remains open.
Last year, the Los Angeles coroner's office changed the cause of Wood's death from "accident" to "undetermined."
Wood, an Oscar nominee known for roles in West Side Story and Rebel Without a Cause, died at the age of 43. She and Wagner, star of TV's Hart to Hart, were married twice: first in 1957, before divorcing six years later, and again in 1972.