In a move likely to renew a longstanding ethical controversy, geneticists are quietly making plans to study the DNA of Adam Lanza, 20, who killed 20 children and seven adults in Newtown, Conn. Their work will be an effort to discover biological clues to extreme violence.

The researchers, at the University of Connecticut, confirmed their plans through a spokeswoman but declined to provide details. But other experts speculated that the geneticists might look for mutations that might be associated with mental illnesses and ones that might also increase the risk for violence.

They could look at all of Mr. Lanza’s genes, searching for something unusual like gene duplications or deletions or unexpected mutations, or they might determine the sequence of his entire genome, the genes and the vast regions of DNA that are not genes, in an extended search for aberrations that could determine which genes are active and how active they are.

But whatever they do, this apparently is the first time researchers will attempt a detailed study of the DNA of a mass killer.