That man told police he occasionally met Klein for dinner or drinks and that she complained Ferrante was controlling and not supportive of her job or her their daughter.
The man said Klein visited him in Boston overnight in June 2012 and attended a medical conference with him later that year in Atlanta and another in San Francisco in February.
Within weeks of her death, police determined Ferrante confronted Klein three times about whether she was having an affair. Other evidence shows Klein "intended to have a conversation with Ferrante and that Ferrante would `not like the discussion,''' police said.
Klein was also an only child and didn't want her 6-year-old daughter to be one too, her mother Lois Klein, 78, of Towson, Md., has told the Pittsburgh Post-Gazette. She said Klein was taking fertility drugs and said police had questioned her about whether Ferrante wanted another child, too.
Klein did not answer her home phone and an answering machine would not take a message Thursday.
Zappala said in a news release that Klein's parents have custody of their granddaughter.
Ferrante and Klein met while she was a student and Ferrante worked at the VA hospital in Bedford, Mass. They were married in 2001. Ferrante worked at Harvard Medical School and Massachusetts General Hospital before moving to Pittsburgh with Klein two years ago to join the university's neurological surgery team.
The university said it is cooperating with the investigation and that Ferrante has been placed in indefinite leave due to the charges. Ferrante has been denied access to the lab since police started investigating Klein's death in May.
A lethal dose of cyanide is about 200 milligrams, about 1/25th the weight of a nickel, said John Trestrail, a pharmacist and expert who taught a class on criminal poisoning at the FBI National Academy.
Cyanide kills by destroying cells.
"In the cells, we have a power plant, so to speak, that produces energy and cyanide basically short-circuits that ability to produce energy, and we can't use oxygen, and the cells die rapidly,'' Trestrail said. "It goes body-wide.''