Joshua Lott for The New York Times
TUCSON — Dr. Bruce Parks unzips a white body bag on a steel gurney and gingerly lifts out a human skull and mandible, turning them over in his hands and examining the few teeth still in their sockets.
The body bag, coated with dust, also contains a broken pelvis, a femur and a few smaller bones found in the desert in June, along with a pair of white sneakers.
“These are people who are probably not going to be identified,” said Dr. Parks, the chief medical examiner for Pima County. There are eight other body bags crowded on the gurney.
The Pima County morgue is running out of space as the number of Latin American immigrants found dead in the deserts around Tucson has soared this year during a heat wave.
The rise in deaths comes as Arizona is embroiled in a bitter legal battle over a new law intended to discourage illegal immigrants from settling here by making it a state crime for them to live or seek work.
But the law has not kept the immigrants from trying to cross hundreds of miles of desert on foot in record-breaking heat. The bodies of 57 border crossers have been brought in during July so far, putting it on track to be the worst month for such deaths in the last five years.
Since the first of the year, more than 150 people suspected of being illegal immigrants have been found dead, well above the 107 discovered during the same period in each of the last two years. The sudden spike in deaths has overwhelmed investigators and pathologists at the Pima County Medical Examiner’s Office. Two weeks ago, Dr. Parks was forced to bring in a refrigerated truck to store the remains of two dozen people because the building’s two units were full.
“We can store about 200 full-sized individuals, but we have over 300 people here now, and most of those are border crossers,” Dr. Parks said. “We keep hoping we have seen the worst of this, of these migration deaths. Yet we still see a lot of remains.”
The increase in deaths has happened despite many signs that the number of immigrants crossing the border illegally has dropped in recent years. The number of people caught trying to sneak across the frontier without a visa has fallen in each of the last five years and stands at about half of the record 616,000 arrested in 2000.
Not only has the economic downturn in the United States eliminated many of the jobs that used to lure immigrants, human rights groups say, but also the federal government has stepped up efforts to stop the underground railroad of migrants, building mammoth fences in several border towns and flooding the region with hundreds of new Border Patrol agents equipped with high-tech surveillance tools.
These tougher enforcement measures have pushed smugglers and illegal immigrants to take their chances on isolated trails through the deserts and mountains of southern Arizona, where they must sometimes walk for three or four days before reaching a road.
“As we gain more control, the smugglers are taking people out to even more remote areas,” said Omar Candelaria, the special operations supervisor for the Border Patrol’s Tucson Sector. “They have further to walk and they are less prepared for the journey, and they don’t make it.”
Mr. Candelaria said the surge in discoveries of bodies this year might also owe something to increased patrols. He noted that some of the remains found this year belong to people who died in previous years. But Dr. Parks said that could not account for the entire increase this year. Indeed, the majority of bodies brought in during July, Dr. Parks said, were dead less than a week.
Human rights groups say it is the government’s sustained crackdown on human smuggling that has led to more deaths.
“The more that you militarize the border, the more you push the migrant flows into more isolated and desolate areas, and people hurt or injured are just left behind,” said Kat Rodriguez, a spokeswoman for the Coalición de Derechos Humanos in Tucson.
At the medical examiner’s office in Tucson, Dr. Park’s team of five investigators, six pathologists and one forensic anthropologist face an enormous backlog of more than 150 unidentified remains, with one case going back as far as 1993.
Every day, they labor to match remains with descriptions provided by people who have called their office to report a missing relative, or with reports collected by human rights groups and by Mexican authorities.
Since 2000, Dr. Park’s office has handled more than 1,700 border-crossing cases, and officials here have managed to confirm the identities of about 1,050 of the remains.
Investigators sift through the things the dead carried for clues — Mexican voter registration cards, telephone numbers scrawled on scraps of paper, jewelry, rosaries, family photographs. Often there is precious little to go on.
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Joshua Lott for The New York Times
“We had one gentleman who came in as bones, but around his wrist there was a bracelet from a Mexican Hospital that had his picture,” said David Valenzuela, one of the investigators.
If no documents are found, the task becomes harder. Many of the deceased immigrants were too poor to have visited doctors or dentists on a regular basis, so no dental or medical records may not exist. Sometimes, a family photograph of the deceased smiling widely is all investigators have to document dental work.
On a recent morning, Bruce Anderson, the forensic anthropologist in the office, was examining the skeleton of an adolescent boy, whose age was somewhere between 14 and 17. His mummified remains were found on the Tohono O’odham Indian Reservation west of Tucson on July 15. The only lead to his identity was a missing front tooth and the neighboring teeth crowded together in the space.
Dr. Anderson called the Coalición de Derechos Humanos, who had a report of a 13-year-old who had been reported missing this year after crossing the border near Sonoyta, Mexico.
The charity immediately contacted the boy’s family to see if he had lost a permanent tooth. Dr. Anderson was still waiting for a reply.
The process takes time, and remains keep piling up. On Monday, Mr. Anderson faced a backlog of 14 new skeletons, in addition to the 40 active cases he is investigating, he said. “One person can’t keep up with this load,” he said.
The pathologists are also under strain. One day last week, Dr. Cynthia Porterfield did five autopsies, on remains of border crossers who died in the desert.
Dr. Porterfield was able to identify one: Jesse Palma Valenzuela, 30, who died on July 12. Three of his travel companions had tried to carry his body back to Mexico but became tired and abandoned him, wrapped in a blanket and positioned off the ground in a tree to keep animals from eating him. Then they crossed back into Mexico and notified the Border Patrol.
Agents discovered Mr. Valenzuela’s body on July 17, right where his friends said it would be, about two-and-a-half miles east of Lukeville, Ariz., not far from the border. Though decomposed, he was still recognizable.
“He’s got quite a few tattoos,” Dr. Porterfield said. “It is how the family ID’d him.”
