The uprising that toppled Gaddafi last month was ignited by protests linked to the Abu Salim massacre.
In February, families of inmates killed at the south Tripoli prison in 1996 demonstrated in the eastern city of Benghazi to demand the release of their lawyer.
Human rights groups have estimated that about 2 000 Abu Salim inmates were killed in the 1996 massacre.
“We are dealing with more than 1 270 martyrs and must distinguish each one from the other for identification by comparing their DNA with family members,” said Dr Osman Abdul Jalil, a medical official.
“It may take years to reach the truth.”