The death of a young boy adopted from Russia at his Texas home was an accident and the bruises found on his body were self-inflicted, a coroner ruled Friday in a case that ignited a diplomatic row.
Russian officials had claimed that three-year-old Max Shatto (born Maxim Kuzmin) was tortured and murdered by his adoptive mother, whipping up a storm of controversy less than two months after Russia banned US adoptions.
But four doctors who reviewed the autopsy results cleared his adoptive parents of wrongdoing, officials said in a statement.
The autopsy concluded that Max -- whose mother found him unconscious in the backyard and rushed him to hospital -- died from a lacerated artery in his bowel due to blunt force trauma in his abdomen.
"Based on all medical reasonable probability, the manner of death is accidental," the Ector County Medical Examiner's Office said.
While Russian officials accused Laura and Alan Shatto of doping the boy with "psychoactive drugs," the toxicology report found no drugs or medicines in his system.
The coroner also noted that Max Shatto had a mental disorder that caused him to hurt himself.
The Ector County Sheriff's Office said it would continue to investigate, along with other agencies.
"We are going to let this investigation take its course and do what is proper and right," the sheriff said.
While the Shattos are cleared of homicide, they could still face negligence charges for leaving the boy alone in the yard.
"They've taken care of the issue of willfulness, that's knowing and deliberate," the family's attorney, Michael Brown, told the Odessa American newspaper.
"They left open any issues of criminal negligence, which I don't think are there either."
The boy's death exacerbated diplomatic tensions triggered by a US bill targeting Russian officials with sanctions over the prison death of Russian lawyer Sergei Magnitsky.
Russia retaliated with a ban on all US adoptions, saying Russian children in the United States were abused and even murdered by their adoptive parents.
Last month, the Russian Duma crafted an appeal to the US Congress saying it would be "unacceptable" for the Shattos to retain custody of Max's younger brother and insisted the two-year-old boy be returned to Russia.
The boys' biological mother, recovering alcoholic Yulia Kuzmina, appeared on a string of popular talkshows, vowing to "fight" for Kristopher (born as Kirill) and claiming she was now ready to raise him.
Neighbors in the 23-year-old's hometown of Gdov of 7,000 inhabitants, 700 kilometres northwest of Moscow on the border with Estonia scoffed at the idea.
"Return her child to her? She can't even be trusted with a dog!" Kuzmina's neighbor Zoya Prokhorova told AFP.
Another neighbor, Nina Serova, said "we have never seen Yulia sober."
US Ambassador to Moscow Michael McFaul responded to the firestorm by calling on Russian officials to stop "sensational exploitation" of the tragic death.
A State Department spokesman said the US government was "saddened by this terrible tragedy."
"Until the investigation by Texan authorities is complete, it would be premature to draw any conclusions," deputy acting spokesman Patrick Ventrell told reporters.
He added that local officials deny providing the Russian government any documents tied to the investigation and that the state's child protective services also dispute statements they said had been falsely attributed to them.
The Texas Department of Family and Protective Services earlier cleared the US agency that facilitated the adoption of any wrongdoing amid allegations that it did not properly screen the Shattos.
The state's child protective services said it launched an investigation of the family in the wake of the boy's death but did not determine it was necessary to remove his two-year-old brother from the home.