This is the room where my whole family was killed, says Safa Younes. Bullet holes pepper the front door to the house in the Iraqi town of Haditha, where she grew up. Inside the back bedroom, a colourful bedspread covers the bed where her family was shot. This is where she hid with her five siblings, mum and aunt when US marines stormed into their home and opened fire, killing everyone apart from Safa, on 19 November 2005.

Now, 20 years on, a BBC Eye investigation has uncovered evidence that implicates two marines, who were never brought to trial, in the killing of Safa's family, according to a forensic expert. The evidence—mainly statements and testimony given in the aftermath of the killings—raises doubts about the American investigation into what happened that day, and poses significant questions over how US armed forces are held to account.

The killing of Safa's family was part of what became known as the Haditha massacre, when US marines killed 24 Iraqi civilians, including four women and six children. They entered three homes, killing nearly everyone inside, as well as a driver and four students in a car, who were on their way to college. The incident triggered the longest US war crimes investigation of the Iraq war, but no one was convicted of the killings.

The marines claimed they were responding to gunfire after a roadside bomb killed one of their squad members. However, Safa argues, We hadn't been accused of anything. We didn't even have any weapons in the house. She survived by pretending to be dead among her siblings. Four marines were initially charged with murder, but conflicting accounts led to dropped charges.

Forensic expert Michael Maloney stated that the evidence points to at least two marines being responsible for the deaths, challenging the assertion that squad leader Staff Sergeant Frank Wuterich was the sole shooter. Video evidence and testimony reveal that Lance Corporal Humberto Mendoza admitted to shooting Safa's father and later contradicted his earlier statements, suggesting he entered the room where the shootings occurred.

Despite this new evidence, Safa and the families of the victims face continued frustration as the US military has stated it would not reopen the investigation unless substantial new evidence is found. Safa, now 33 with her own children, continues to seek justice, stating that the lack of accountability reflects an ongoing crime against her family.