Another of Ellis' ex-girlfriends, who has name suppression, told the court she lived with him in 2006.
She said he was using methamphetamine and later began drinking heavily.
The woman described a violent relationship and said on one occasion Ellis kicked her from behind before dragging her down the hallway by her hair.
"Then he got me up on the kitchen counter and was strangling me.''
She said Ellis' hands got tighter and she struggled to breathe.
"I thought he was going to kill me, for sure. I thought: There is no way I'm going to get out of this. He's a lot stronger than I am. I was just terrified, really.''
The woman said she managed to kick him away and he called his parents.
She told the court of two other attacks where she was thrown against a bookcase and a computer table.
The woman said during another incident Ellis phoned police. She said the next day he told her: "You're f****** lucky I called the cops, b****. I was going to kill you.''
Ellis' lawyer John Anderson put it to the woman that the strangling incident never happened.
She responded: "I don't want to be here right now. I'm not doing this for myself, I'm doing this for her,'' referring to Ms Blackbourn.
Four years later the man was in a relationship with Ms Blackbourn.
In her opening, Ms Buckley said Ellis was "obsessed'' with Ms Blackbourn but Ms Blackbourn had found a new man.
"In a desperate attempt to try and get her back, he even tried to self-harm. That did not work, in fact that drove Ms Blackbourn away.''
Ms Buckley alleged that on the night of the murder, Ellis took a knife from his home and drove to Ms Blackbourn's house in Glenfield. He parked 200 metres away and walked the rest of the way.
"She was raped, strangled and stabbed to death by her ex-partner, the accused ... After killing her, he set her body on fire. She was 43.''
Ms Buckley said Ellis stabbed Ms Blackbourn so hard that the knife went through her sternum.
The trial is set down for three weeks and is due to hear from 38 witnesses.
