It all matches: the gap-toothed smile in the photograph looks just like the gap in the skull. The age on the voter card matches those of the remains. The sun-bleaching of the 44 bones coincides with the amount of time the illegal border crosser has been missing.

It is enough to convince the medical examiner that the remains found in May in the Cabeza Prieta National Wildlife Refuge southwest of Tucson are those of Jesús Alberto Cabral López. The 22-year-old laborer left Villa Juárez, Sonora, on May 8, 2006, hoping to cross into the United States and find a job better than the $50-a-week farm work that awaited him at home.

For Jesús' family, the long-awaited determination ends nearly 15 months of searching and sadness. They're among the lucky ones: The Medical Examiner's Office says nearly one-third of the 1,137 bodies found in the desert near Tucson in the past seven years remain unidentified.

In many cases, a positive outcome requires comparing genetic material of the deceased against the mitochondrial DNA of someone believed to be a female relative. This type of DNA testing can only confirm a suspected identity; there is no general database to run results through, so a positive ID is possible only by comparing a corpse's DNA with that of a possible relative.

DNA testing is complicated and lengthy — it can take up to 360 hours and sometimes stretch over a year or more. Even then, sometimes it has to be repeated. But that's not the main reason families wait so long for the results that could finally end their uncertainty.

The tests are done at a forensics lab at Baylor University in Waco, Texas, rather than in Pima County, which accounts for about 85 percent of the cases Baylor receives for analysis. Their cost, about $2,000 per case, is paid by the Mexican government.

An additional hang-up stems from Mexico's requirement that each time a Mexican consulate requests a DNA analysis, it must route it through the consulate in Austin, Texas, which processes bone samples from the deceased and blood samples from family members in Mexico. Once the testing begins, Baylor scientists are required to report results to and communicate with the Mexican government and not directly with the consulates handling the cases.

Some advocates and academics in Tucson are pushing to speed up the process by moving DNA testing to Tucson, possibly to the University of Arizona.

DNA sometimes last hope

Jesús' family could have sought DNA analysis, but chooses instead to accept the medical examiner's identification, largely based on dental comparisons of the remains with photographs of their son. They turn from the search for their son to the task of bringing him home.

But for many Mexican families whose loved ones have gone missing on the border, a DNA match is their last hope.

The job of tracking samples from families and those of the unidentified dead is done through Mexico's System for the Identification of Remains and Locating Individuals, or SIRLI, a database created in April 2005 that links Mexican consulates in the United States with Mexico's Secretariat of Foreign Relations. The database also contains reports, photographs and other documentation on people who are missing, as well as a registry of people known to have died in the United States.

It's the same system the Mexican Consulate in Tucson used to locate Jesús' brother Antonio, who had reported his younger brother's disappearance to the consulate in San Bernardino, Calif.

Work is under way to expand the SIRLI database to include DNA profiles of all cases without a name association, says Juan Manuel Calderón Jaimes, the Mexican consul in Tucson.

The intent is that in the future, the database will allow DNA samples from unidentified remains to be compared with genetic information from families searching for missing loved ones, Calderón Jaimes says. To prepare for that day, the Pima County Medical Examiner's Office is already collecting genetic samples from unidentified bodies and sending them to Baylor for testing and storage.

40 cases solved with DNA

The agreement between Mexico and Baylor University for DNA testing was formalized in late 2005.

"Mexico has been criticized because people think nothing is being done to help people," says Baylor anthropology professor Lori Baker, who heads the DNA project.

"They are doing a lot," she says. "They are investing lots of money, and they paid for the creation of the (SIRLI) database."

Since the agreement began, Baylor's DNA lab has solved 40 of the more than 300 cases referred to it. The lab can handle up to 400 cases a year, Baker says.

Testing is complex and highly detailed. There are five steps, beginning with the selection and cleaning of the bone sample, using bleach and sandpaper to remove external contamination.

Next, the sample is cut into smaller bits and placed in sterile bags. The samples are cleaned again before being ground down to prepare the material for DNA extraction.

The extraction is done either with chemicals or mechanically by breaking down the bone material until genetic material is released.

Baylor uses a mechanical process that freezes ground bone in liquid nitrogen and then grinds it to a powder. A chemical broth pulls DNA from the powdered bone by breaking open the cells. A different chemical mix binds to the DNA.

Once the DNA is isolated, it is placed in a machine that amplifies and copies it to ensure there is enough material to analyze.

The effectiveness of the process depends on the quality and condition of the bone sample.

One unexpected challenge is the issue of trust — the very tool created to ease identification causes families to fear the information will be used to hunt down and deport illegal residents of the United States. The information is used for identification purposes only.

"We are not building a database of illegal immigrants," Baker says.

Move, modify testing, some say

Despite the success of the DNA testing, Mexican Consul Calderón Jaimes says moving it to Tucson could speed up the process.

"It just isn't as fast as you would wish it to be and that is why we are looking for alternatives," he says.

He has some support.

Liz Wood, a researcher at the University of Arizona, and Kat Rodriguez of the Human Rights Coalition are working on a proposal to move the DNA testing to Tucson and use a different type of genetic testing than the mitochondrial DNA analysis now used at Baylor.

"Mitochondrial DNA is wonderful for certain applications, especially if you have an idea of who the individual might be," Wood says. "But with mitochondrial DNA you cannot do blind matches that allow testing on people whose identities are completely unknown."

Wood's proposal includes building two databases, one with information about the deceased and another with information about families whose loved ones are missing. The two would run against one another, searching for a match.

It is unclear who would pay to develop the database and whether there would be a cost to move it, but Mexico likely would pay for continued DNA testing. Mexico did not pay to set up testing at Baylor because the university already had a forensics lab. The UA has a forensics lab, too, but it isn't yet known if it could accommodate the DNA testing now being done at Baylor.

Mexican Consul Calderón Jaimes said he already has sent a summary of the proposal to the Secretariat of Foreign Relations in Mexico for consideration, but there is no indication whether or when a decision would be made.

There are plans to present the proposal to the Pima County Board of Supervisors later this year.

"The idea is to identify people more quickly," Rodriguez says. "If the majority of the crossings are happening here, and the majority of the bodies are found here, it would be beneficial to have a local project."