A jury in Atlanta, US, found him guilty on 10 counts after a they spent just 90 minutes deliberating the case.Blackwell showed no emotion as he was jailed for 40 years.
Mr Tolbert and Mr Gooden were at home together on February 12 when Blackwell broke in to their house and poured hot water all over their bodies.
Mr Marquez, 21, suffered severe burns to his face, neck, arms and back that required skin graft surgery.
"The pain doesn't let you sleep. It's like excruciating, 24 hours a day and it doesn't go anywhere. It doesn't dial down or anything. It's just there,"
"You wake up in the middle of the night, you just cry because you want to sleep and you can't."
The attack was committed by Blackwell, who was Mr Gooden's mum's boyfriend.According to a police report obtained by WSB-TV, Blackwell was disgusted by the couple's relationship.
"They'll be all right. It was just a little hot water on them," he reportedly said.
So far almost £20,000 has been raised online for the duo.