They were Teresa Cormack, 6, killed in 1987 by Jules Mikus, and Kylie Smith, 15, raped and murdered by Paul Bailey in 1991.
"We stopped our kids biking to the river," Mr McVicar remembered of the former case.
Mikus was not charged until advances in DNA technology enabled his arrest and conviction in 2002. In the Smith case, Bailey was out on bail at the time for an attempted rape of an older woman.
Mr McVicar said the Sensible Sentencing Trust was effective in mobilising public opinion and influencing politicians.
"We drive change. We are the squeaky wheel," Mr McVicar said. "We don't get the credit for changes but that's not what we want -- it's the change we want."
Since its inception in 1992, the Sensible Sensible Trust has pushed for some changes that have been adopted, such as a longer minimum prison sentence for murder -- from 10 years to 17 years -- giving victims a say at sentencing, and putting public safety at the forefront of a judge's decision on whether to grant bail.
There have also been changes to parole law, with parole boards now given the power to put annual hearings on hold for three or even five years.
Mr McVicar said parole was a "cruel mechanism -- a barbaric way of unloading prisons", with victims having to "argue their case" every year as prisoners became eligible for parole.
The Sensible Sentencing Trust was now involved in a review of the youth justice system, he said.
