Johnson said: "I can honestly tell you that we did not discuss." Roux replied that when a witness uses the word "honest" it makes him nervous.
Pistorius has admitted to killing his girlfriend, shooting at her through a toilet door. However, he says he thought he was shooting at an intruder.
The trial is being aired live, although some witnesses' faces are not being shown. Their voices can be heard.
Pistorius can be seen, often taking notes, sometimes holding his head in his hands.
The mother of Reeva Steenkamp was shaken after Pistorius failed to "look her in the eye" at the start of his murder trial in Pretoria.
On Monday June Steenkamp came face-to-face with Pistorius for the first time since her daughter was shot dead on Valentine's Day last year.
She said the Olympian and Paralympian "Blade Runner" ignored her presence as he sat in the dock taking notes.
"I wanted to see him and him to see me," she told ITV news. "But he didn't look at me or anything. He just walked straight and looked ahead.
"The whole point was he must see me, that I'm there," she added. "I'm her mother and, you know, what happened to her was terrible and I just wanted him to see me there. I'm there representing Reeva."
Steenkamp said she "wishes she could have been there" to protect her daughter after learning about the trauma and pain she went through. Reeva Steenkamp was hit by three 9mm pistol bullets in the head, arm and hip.
"That was the time I broke down. The screaming ... you know. That was my child there that was screaming, that was injured and dying."
Earlier, she had told reporters she was prepared to forgive the athlete despite losing her "precious" daughter Reeva. "It's actually important to forgive him for me, because I don't want to live with bitterness in my life," she told the Today show.
"It would become my whole being. I don't want that."
She was not in court yesterday when Pistorius broke down after his defence team described the severe brain damage Reeva Steenkamp sustained.
The athlete's defence counsel, Barry Roux, landed significant blows against the testimony of Michelle Burger, a neighbour who claimed she heard Steenkamp's blood-curdling screams, followed by the sound of gunfire, the night she died.
Roux challenged her testimony, signalling that the gunshots left Steenkamp's brain so "damaged" she couldn't have screamed. Pistorius wept in the dock and covered his ears with his hands.
"You tell us from 177m you could hear that screaming," Roux continued. "It was so distinct, what you could hear, that you could hear increased emotion, increased intensity?
"That person, who had sustained that amount of brain damage [when the fourth bullet struck her in the head], would have no response, no cognitive function. There can have been no response and yet you claim to have heard her screaming?" Roux said.
A second witness, Estelle van der Merwe, a neighbour, told Pretoria's High Court she heard people arguing just before 2am the night Steenkamp was killed, followed by the sound of what she described as four "shots or explosions".
On Monday, Pistorius pleaded not guilty to murdering Reeva Steenkamp, claiming he shot her in a case of mistaken identity thinking she was an intruder.
Prosecutors argue he intentionally shot and killed his girlfriend after a domestic dispute. If convicted of murder he will almost certainly receive a life sentence, with a minimum term of 25 years. Independent
