By Mica Rosenberg
MEXICO CITY (Reuters) - Alejandro Espinoza knew his brother and nephew were dead when he saw the photo in the newspaper, their bloodied bodies slumped in a pile of 72 migrants massacred in northern Mexico by the Zetas drug gang.
But his pain was only made worse when Mexican investigators shipped the wrong body home to his family in Honduras.
Thousands of drug war corpses have exposed the gaps in Mexican forensic science, where teams struggle to identify victims, vital evidence is often overlooked and most murders go unsolved -- a far cry from the United States.
"We went to the airport to get my nephew Carlos," Espinoza said. "But they sent the body of an indigenous guy and my nephew was black. They later said that body was a Brazilian."
"We came with the intention of burying them together but couldn't," he said of his relatives, whom the Zetas killed last year. "We trusted in the Mexican forensic officials. They were irresponsible. But the only thing we can do is be angry."
Physical evidence is used in less than 8 percent of Mexican convictions in closed-door hearings based on written affidavits. More than 70 percent of homicides go unsolved.
By contrast, FBI figures show two-thirds of U.S. murders were solved in 2009, the latest year with full data.
Mexico's record may improve thanks to reforms to the justice system to shift to oral trials like those in the United States by 2016.
In the new system, forensic experts will present evidence from autopsies and crime scenes in an open court to be argued over by prosecutors who in the past relied on confessions, sometimes drawn out by police beatings or torture.
President Felipe Calderon last week acknowledged the "murky conditions" used to collect evidence when he inaugurated new forensic laboratories for the federal police.
"The proof of a homicide shouldn't be a statement from the person who committed it," he said. "The proof should be the weapon used in the murder. The proof should be hair samples, sweat samples, genetic evidence found on the victim."
The $35 million labs in Mexico City are part of the colossal effort needed to train lawyers, judges and police to adapt to the new procedures in just five years.
U.S. experts are lending a hand, spending $23.5 million on training and equipment to bring federal forensic labs and crime scene analysis up to international standards.
BODIES AND BACK-HOES
But the bodies keep piling up, often faster than examiners can manage. More than 40,000 people have died in drug violence since late 2006 when Calderon went to war against the cartels, some of whom have taken to preying on vulnerable migrants.
Since April, authorities have dug up nearly 200 bodies in shallow graves in the same municipality where Espinoza's relatives and 70 other migrants were shot. Mass graves found in Durango state the same month have so far yielded 252 bodies.
Police and the army used backhoes to excavate dozens of bodies in Durango before prosecutors told them to stop.
"Valuable evidence was lost," said a source from the federal attorney general's office.
Over 150 of the Durango bodies have since been reburied in anonymous graves. Only three have been identified.
"This type of thing has never happened in the country. We were completely overwhelmed," said Heraclio Garcia, director of investigations at the state prosecutor's office.
Garcia said his offices are equipped to take in three or four bodies a day but are receiving up to 15. The storage facility has capacity for only 20 bodies, forcing Durango to contract mobile freezer units to hold the rest.
Hundreds of grieving family members are lining up at medical examiners offices to give DNA samples in the hope there will be a match with one of the nameless bodies.
Nobody knows just how many people have gone missing because no reliable statistics exist but the national human rights' commission estimates at least 5,000 Mexicans have disappeared in the drug war.
The government wants to create a national DNA database to help identify the missing by comparing the remains of some 3,000 unidentified corpses processed each year with genetic samples from families.
But it will be a challenge to standardize protocols that can differ radically from state to state, says the Red Cross, which is helping to modernize Mexico's forensics system.
Many cases are unsolved because scared families shy away from reporting disappearances. In San Fernando, municipal police were accused of shuttling victims to be massacred.
Drug gangs have been known to return to crime scenes and break into morgues to steal the bodies of dead comrades.
"There have been reports in several states ... of threats and attacks against criminal investigators and forensic experts," said Morris Tidball-Binz of the Red Cross. "Sometimes there isn't any access to the scene at all."
(Additional reporting by Gustavo Palencia in Tegucigalpa; Editing by John O'Callaghan)