GUATEMALA CITY, June 17 (Reuters) - Guatemala opened its first DNA testing lab on Wednesday hoping that genetic fingerprinting will help solve decades-old civil war crimes as well as more recent murders.

Guatemala's Forensic Anthropology Foundation opened the $1.5 million laboratory funded by international donations to identify victims excavated from hundreds of mass graves from the 1960-1996 civil war.

More than a quarter million people -- mostly Mayan villagers -- were killed or disappeared during the civil war that pitted successive right-wing governments against leftist guerrillas.

A U.N.-backed truth Commission found that Guatemalan security forces committed more than 90 percent of the killings but only a few officials have been tried for war crimes.

"This work will allow the families of the victims to answer the questions we have: what happened in Guatemala, who was responsible, and how can we bring them to justice?" said Julio Solorzano, desperate to find out what happened to his mother who disappeared in December 1980 after being picked up by military police.

Solorzano gave his own DNA sample with an oral swab which will go into a database of victims' family members to be matched with samples from thousands of bodies exhumed by anthropologists.

While the bulk of the work will focus on past crimes, Guatemalan authorities are eager to use the lab to aid the country's ailing justice system, which only manages to prosecute 2 percent of the 6,000 murders committed each year.

Since the end of the war, Guatemala's population of 13 million has been overrun with violence by youth gangs and Mexican cartels increasingly using Central America as a corridor to smuggle drugs north to the United States.