A panel beater who shot dead an intruder after smoking up to 68 bongs and drinking about 40 stubbies had no right to be "judge, jury and executioner," a court has heard.

Patricia Vandenberg told the Supreme Court on Tuesday her world was turned upside down when Ivan D'Angelo took the life of her only son, Wade, nine years after she lost her husband to bowel cancer.

Shot dead: Wade Vandenberg. Credit:Courtesy Victoria Police

Mrs Vandenberg said Mother's Day was now spent at the cemetery so she could be close to her "beautiful boy".

The mother of three told Justice Lex Lasry that she would regularly sit in her son's bedroom because "it still smells like he is here".