Within weeks of the September 2014 disappearance of 43 college students, Mexican authorities had rounded up scores of suspects and announced they had solved the case.
At a hastily called news conference, prosecutors showed video of drug gang members confessing to taking the students from police, then slaughtering them and incinerating the bodies at a junkyard and dumping the evidence in a river.
Two independent, international teams of experts subsequently cast doubt on the official investigation. Now, the government case has suffered another blow: Accusations of torture.
In previously unseen court documents obtained by The Associated Press, 10 of the suspects described a chillingly similar script: First the questions, then the punches, electric shocks and partial asphyxiations with plastic bags; then, finally, the threats to kill their loved ones unless they confessed to stories that backed up the government's line.
Some said they were given planted evidence or prefabricated stories to support the government's conclusions.
Medical reports published last month by the Inter-American Human Rights Commission appear to confirm the allegations of torture. Of the 10 case files obtained by the AP, the group reviewed five, and it found credible evidence of torture in all of them.
"They were giving me electric shocks in the testicles and all over my body," one of the suspects, Patricio Reyes Landa, a gang member who was detained a month after the students vanished, told a judge in July, according to the documents obtained by AP. "All this time, it was about two and a half hours, I was blindfolded and they were hitting me."
"A person came up and took off my blindfold and showed me a photo of my family — my two daughters, my wife and my brother," he said. "He said if I didn't do everything they told me to, they were going to rape my daughters. ... I told them I was going to do everything they asked."
Reyes Landa's testimony is crucial to the government case because he was among the first to confess to killing the students and burning their bodies at a dump in the town of Cocula, before their charred remains were tossed in the nearby San Juan River. Apart from those confessions and a single bone fragment that was linked through DNA testing to one of the students, the prosecution has almost no other evidence.
Under Mexican law a confession obtained by torture is not admissible in court.
"If the confessions are tossed out and there is no other evidence, basically there is no case," said Denise Gonzalez, a specialist in human rights and international law at Mexico's Ibero-American University.
The widely held belief that Mexican security forces use torture in drug crime investigations was reinforced by video of an unrelated case circulated on social media last month. It showed a female soldier and a federal police officer interrogating a young woman while they smothered her with a plastic bag until she nearly passed out. The army confirmed the authenticity of the footage, which it said occurred during a massive February 2015 troop deployment to combat drug cartels.
In the case of the missing students, the torture allegations involve federal police or government troops who arrested the suspects on suspicion of ties to the notoriously violent Guerreros Unidos drug cartel. Prosecutors say gang members killed the students after they were handed over by local police who had arrested them in the city of Iguala.
Medical reports among the documents seen by the AP support the torture allegations.
One, by prosecution doctors who examined Reyes Landa two months after he was detained, said he had bruises, scrapes, scabs and "lesions made by a pointed object, similar to those caused by the application of electric devices to his abdomen and thighs."
Just as chilling are claims by alleged Guerreros Unidos gang leader Sidronio Casarrubias, who said a detective with the prosecutors' office abused him for hours after his arrest in February 2015.
"This man here was one of the first to torture me," Casarrubias said, according to the documents as he pointed to the detective, Gabriel Valle Campos.
"He sat on my stomach and asphyxiated me with black plastic bags. And he raped me with a metal object," Casarrubias said. "He threatened to torture my family, my children, the same way he was doing to me."
Eber Betanzos, an assistant prosecutor who is overseeing the government's case, said he could not comment on the allegations, adding that it's up to judges to evaluate a battery of psychological and physical assessments undertaken by some 90 suspects who claim they were tortured. A total of 136 suspects were arrested, charged and are undergoing trials.
Betanzos said 32 of the cases have enough evidence to start criminal investigations, mostly involving accusations of torture "against arresting agents other than the prosecutors' office" — meaning federal police or government troops.
He said the attorney general's office has opened nine investigations so far, mostly involving "injuries that leave marks," including bruises and abrasions.
Attention has focused on Agustin Garcia Reyes, the first suspect to identify the San Juan River as the location where the students' charred remains were dumped — and where the lone piece of physical evidence linked to the students was said to have been found.
The international group of experts raised questions about his testimony after videos and photos surfaced showing Garcia Reyes walking around the river with Tomas Zeron, the head of the detectives' agency, the day before prosecutors said bone fragments were found there.
That led to suspicions the evidence was planted. Amid the accusations of dirty tricks, Zeron released a video of his own showing himself at the crime scene with Garcia Reyes but not removing or finding any bones. That was in line with prosecutors' claims that the remains were found the next day by divers.
In the documents obtained by the AP, however, Garcia Reyes said he was tortured for hours and coached on what to confess when he was taken to the river about a month after the students disappeared.
"They put a bag over my head and they began to hit me, and I told them I didn't know anything," Garcia Reyes said in the court document. "They said, 'You'd better tell us where they are, because if you don't we're going to kill your wife, your son and you too.'"
"They took me to the river, and in the truck on the way there they said, 'Now, you're going to act like you threw the bags (of remains) into the river, and if you don't, we're going to keep hitting you.'"
"We reached the spot and they were taping it, and I acted as if I had thrown the bags into the river, and then they took me to where there were some plastic bags, and I pointed to them as if I was familiar with them."
Despite his accusations of torture, however, Garcia Reyes can be seen walking normally in the prosecutors' video, without any visible signs of abuse.
Gonzalez, the university human rights specialist, acknowledged that it's possible some suspects might make up stories of torture.
But, she added, "in the context of Mexico, where torture is generalized ... every allegation should be investigated because, given the context, it is very possible they are true."