michael usher , the veteran journalist who conducted the interview , has revealed her walked away from the experience ` totally drained and realising that there are a lot of broken people ' .
he also admitted that despite all the revelations about his son 's abusive ways , mr polkinghorne could still not understand why his son was dead .
jessica silva speaks publicly for the first time about the day , mother 's day 2012 , when she stabbed and killed her partner , the father of her young son .