Ms Batty has told the inquest into Luke's death that he seemed buoyed by seeing his father in such good spirits.
"My impression was that they'd had a really good exchange," she said this week.
"I thought, why not let Luke, after so much trauma, have a hit with his father."
The murder occurred, the inquest heard, because Anderson succeeded in isolating Luke from the groups of parents and children at the ground.
Anderson clubbed his 11-year-old son with a cricket bat then attacked him with a knife, as they played together in the nets.
Anderson, covered with blood and holding a knife, lunged at police and paramedics.
He was shot by police and told paramedics "let me die" as they tried to treat him. He died in hospital.
There were multiple arrest warrants for the 54-year-old, who also faced child pornography charges, when he attacked Luke.
He was in breach of a supervision order which, Ms Batty did not realise, restricted his access to Luke to weekend sporting events.
He was also the subject of an intervention order after threatening to behead his housemate.
Ms Batty says had she known about that intervention order, she more likely would have called police the day Luke died, on February 12.
Ms Batty wept as she said she'd given police Anderson's address weeks before he attacked Luke and wondered: "Why haven't you arrested him, I've given you his bloody address."
"The man was never important enough, he wasn't f***ing dangerous enough, he wasn't bad enough until now. Now he's the worst," she told the Victorian Coroners Court.
The inquest heard police did have the opportunity to arrest Anderson two weeks before he killed Luke and were well aware of his reputation as a violent, unstable man.
Aware of his unpredictability, four officers arrived at his home on January 27 to serve the intervention order on him for threatening his housemate.
The officers conducted the relevant background check on Anderson in the police database but found no record of the outstanding warrants.
The warrants weren't in the system yet, so they didn't know their colleagues at another station had been looking for Anderson.
Police had variously described Anderson as "abnormal" and "paranoid", with one officer saying "going postal would definitely apply to this bloke".
Yet Ms Batty said she was too often left to stand up to Anderson on her own.
She described one occasion in April 2013 when police didn't arrest Anderson hours after a magistrate said Luke could end up as collateral damage in his father's troubled life, and put in place an order preventing contact between the pair.
Anderson had also triggered a warrant for his arrest by failing to show up to court to face an assault charge on the same day.
When he turned up at Luke's football training Ms Batty called police to have him arrested.
She said she became hysterical when they told her they couldn't act because the warrant hadn't been sent through from the court.
Ms Batty's exasperation at her experience with police and social workers was a consistent theme in her two-and-a-half days giving evidence to the inquest.
She described the Department of Human Services as well-meaning, but ultimately ineffective.
"I wanted support. I wanted other people to step in to make some decisions so it wasn't just me facing Greg," she said.
"The only suggestion they have is to have counselling.
"No one spoke to Greg. If he stopped being violent, I wouldn't need counselling.
"Why are they called child protection if they're not someone you can go to to say 'how can I protect my child'?"
Asked repeatedly what she might have done differently in the lead up to Luke's death, Ms Batty began to yell.
"Isn't it unfair that I'm having to be the one to answer for all this?
"Did I ever think Luke would get smacked over the head with a cricket bat and stabbed to death? Of course I didn't.
"So don't ask me any more about what I did and the risk I thought there was, because there was an ongoing, never-ending consideration of Luke's safety, except he got killed, he got killed on a day everyone thought he was fine."
Ms Batty described Anderson as loving and over-protective toward Luke.
She said only after he showed his son a knife and told him "this could be the one to end it all" in April 2013 did she begin to have concerns about what he could be capable of.
But never did she think he was capable of murdering their son.
Luke should have been safe in a public place like a cricket oval.
"That image of him harming him couldn't happen in a public place," Ms Batty said.
"It couldn't happen at the Tyabb oval but it bloody did."
For Ms Batty, Luke was everything, the centre of her life.
Now she hopes the inquest will help prevent anyone else suffering the same tragedy.
"I made the best decisions I could at the time," Ms Batty said.
"No one loved my son more than me.
"And I'm still sitting here trying to make it better for him and I'll never get him back.
"All I can do is make sure that some people, out of all of this, learn.
"I could have made different decisions, and I wish I had. But in the future, different decisions can be made."
- AAP
