Naposki showed no emotion as the prosecutor presented the court a photo of McLaughlin's body.
Prosecutors said Johnston stood to collect $1 million in life insurance from his death.
"Mr. Naposki had no money, and Nanette Johnston, outside of Bill McLaughlin, also had no money," prosecutor Matt Murphy said.
Naposki, 44, of Connecticut and Johnston, 45, were arrested in 2009 after the cold case investigation was reopened.
Prosecutors allege Johnston convinced Naposki to kill McLaughlin in December of 1994, providing Naposki with keys to the home in the gated community where she had been living with the victim.
McLaughlin was shot six times. McLaughlin's son heard gunshots and found his father's body in the kitchen.
"One second after Bill McLaughlin's heart stopped beating, Nanette Johnston became a millionaire, at least on paper," Murphy said.
Johnston pleaded guilty to grand theft in 1996 for writing forged checks from McLaughlin's accounts without him knowing it. She stole nearly half a million dollars before and after his murder.
The prosecutor said evidence will show Naposki had access to the house key, a silencer made for his gun before the murder and told at least one witness he wanted McLaughlin dead.
Naposki played linebacker in the late 1980s for the New England Patriots and Indianapolis Colts.