University of Pittsburgh researcher Dr. Robert Ferrante is on trial for the murder of his wife, renowned neurologist Autumn Klein.
Prosecutors say he killed her with a cyanide-laced energy drink.
Yesterday police detectives testified they found at least one container of the poisonous drug in Ferrante's lab.
And prosecutors say Ferrante purchased that same drug just two days before his wife's collapse.
Those attending the trial say Ferrante has remained stoic, showing no emotion.
Prosecutors believe the couple considered having a second child, and that the 66-year-old Ferrante told his 41-year-old wife to drink a tainted cocktail, telling her it would help with fertility.
Newly released surveillance video shows Klein leaving work in April 2013. 30 minutes later she was collapsing at home.
The motive, according to prosecutors? They say Ferrante didn't really want to have more kids, and that he suspected his wife was having an affair.
Ferrante has pleaded not guilty to the murder.
His defense team says there's no proof he gave his wife a lethal cocktail, and that her death was either suicide or remains a mystery.