For children and adolescents who die by suicide, the team interviews not just parents and guardians, but also several close friends. In some cases, Dr. Staley recalled, friends knew about the deceased’s struggles with sexuality, gender or drug use that the parents did not.

These conversations can be exceedingly difficult. John Blosnich, head of a research initiative called the L.G.B.T. Mortality Project at the University of Southern California, has done ride-alongs to observe and train death investigators on the importance of collecting data on gender and sexuality. His training also helps investigators navigate distress or stigma about the questions from the deceased’s friends and relatives.

“They’re talking with families who are in shock, who are infuriated, who at times are catatonic because of their loss,” Dr. Blosnich said.

So far, Dr. Blosnich has trained investigators in Utah, Nevada, Colorado, New York and California, where a 2021 state law started a pilot program to collect data on sexual orientation and gender identity. In a recent study of 114 investigators in three states, Dr. Blosnich reported that only about 41 percent had directly asked about a deceased person’s sexual orientation, and just 25 percent had asked about gender identity, before going through the training.

Medical examiners send reports of homicides and suicides to the Centers for Disease Control and Prevention, which maintains a database of violent deaths with extensive demographic, medical and social information, including toxicology tests, mental health diagnoses and even stories of financial and family hardships. But a study of more than 10,000 suicides among young adults reported to the C.D.C. database found that only 20 percent included information on the deceased’s sexuality or gender identity.