Rep. Duncan Hunter is hoping that the fourth time's the charm for fallen Marine Sgt. Rafael Peralta.

The lawmaker, a California Republican and veteran Marine officer, sent a letter Monday petitioning Defense Secretary Jim Mattis to review Peralta's nomination for the Medal of Honor -- a nomination that three previous defense secretaries have opted not to approve.

Unlike his predecessors, however, Mattis has additional reason to be familiar with Peralta's case, having commanded troops as a Marine general in Fallujah, Iraq, during the same time period in which Peralta was killed in action.

Peralta was posthumously awarded the Navy Cross for pulling a live enemy grenade under his body to save fellow Marines during a 2004 house-clearing mission in Fallujah, according to his official medal citation.

Such an act would typically merit the Medal of Honor, and it did in the case of Cpl. Kyle Carpenter, who absorbed much of a grenade blast in Afghanistan in 2010 to save a fellow Marine.

But experts consulted on Peralta's nomination have said the physical evidence of his heroism does not meet the stringent standards for the military's highest valor award. Peralta was wounded by a bullet ricochet to the back of the head immediately before his death, and some investigators have questioned whether he could have been conscious and able to grab the grenade after sustaining that wound.

"The benefit of Secretary Mattis [reviewing Peralta's case] is that he's commanded Marines in Iraq and he knows better than anyone in government right now -- along with [Homeland Security] Secretary [John] Kelly -- how politics can be infused in a valor award case and how the bureaucracy if left unchallenged will win every time," Hunter spokesman Joe Kasper said in a statement provided to Military.com.

"Mattis is still at heart a U.S. Marine and he's well aware that the Marine Corps, as an organization, fully endorsed Peralta's Medal of Honor," the statement said. "Names like Mattis, Kelly and Dunford regularly came up as supporters of the award, but now it's a new administration and there's new hope for the Marine Corps, the Peralta family and anyone else who's been passionate about Peralta's legacy."

Mattis commanded 1st Marine Division during the 2003 invasion of Iraq and subsequent operations early in the war, playing key leadership roles during the first and second battles of Fallujah in the spring and fall of 2004. Peralta was assigned to 1st Battalion, 3rd Marines, part of 3rd Marine Division, at the time of his death.

A spokeswoman for the office of the secretary of defense, Laura Seal, said the office would not comment on the letter, as is policy with congressional correspondence, but would respond directly to its author.

Hunter's letter comes days after the Navy took ownership of the USS Rafael Peralta, an Arleigh Burke-class guided missile destroyer named in honor of the fallen Marine. In light of the ship's delivery, Hunter asked Mattis to re-examine the case that has troubled Peralta's family members and fellow Marines for more than a decade.

"Multiple eyewitnesses conveyed that from their respective fields of view, Peralta initiated several movements toward the grenade and pulled it into his body," Hunter wrote. "In the spirit and tradition of the Medal of Honor, these eyewitness accounts are exceedingly sufficient, but they were overridden based on questionable forensic evidence assembled by Pentagon bureaucrats."

The decision to downgrade Peralta's award, Hunter continued, "still stands in direct contradiction" to evidence unearthed in the Marine Corps official investigation into his death and other evidence, including an independent pathology report.

Defense Secretary Robert Gates, who first reviewed Peralta's case in 2008, wrote in his 2014 memoir "Duty" that he had initially approved the Medal of Honor for Peralta, but reversed his decision after a team of pathologists concluded the Marine could not have acted consciously to stifle the grenade after sustaining his head wound.

His successors Leon Panetta and Chuck Hagel both re-examined Peralta's case at Hunter's request in 2012 and 2013, but each ultimately determined that the margin of doubt remained too great to approve the award.

Eyewitness accounts remain a sticky point in the Peralta case. Hunter notes that three Marines who were there in Fallujah during the firefight credit the sergeant with saving their lives. But a 2014 Washington Post report quoted two Marines who alleged the account of Peralta's heroism had been made up in the minutes after his death, likely out of fear that he had died as a result of a friendly fire incident.

Hunter, who points to evidence including Peralta's shrapnel-scarred rifle, which was underneath him at the time of the blast, and the grenade fuse, recovered from the center of Peralta's body armor, wrote that the grenade could not have detonated six to 10 feet from Peralta's right leg, as Pentagon officials have stated.

"According to the Pentagon's previous logic, the grenade fuse would have needed to travel under and through the concrete floor, as well as the fragments of shrapnel that damaged his weapon," Hunter wrote. "You and I are both well aware that this is impossible and such logic equates to nothing more than a convenient excuse not to award Peralta the Medal of Honor."

The Pentagon is completing a review of valor medals awarded to troops who served in Iraq and Afghanistan launched last year to ensure that those who deserve upgraded awards receive them.

Navy Secretary Ray Mabus has said he's recommended two troops for upgrade to the Medal of Honor, though it remains unclear whether Peralta is one of those two.

Peralta's immediate family long refused to accept Peralta's Navy Cross, maintaining he deserved the higher award. But in 2015, they accepted the medal in a special ceremony, saying they planned to donate it to the destroyer Peralta in tribute.

But Peralta's sister, Icela Peralta Donald, told Military.com last year that she held out hope that her brother would receive the honor she believes he is due.

"My whole entire family knows that one day, Rafa, my brother, is going to get the Medal of Honor," she said. "Hopefully, not only my brother, but all the people who deserve to be awarded will get it."

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at@HopeSeck.