The rates are actually quite high and here is an article with some well known cases http://www.theage.com.au/comment/parole-board-failures-a-matter-of-life-and-death-20130824-2sike.html
48.6 percent of unsupervised offenders will reoffend while only 43.6 percent of supervised offenders will reoffend. At 36 months after release, the estimated reoffending rate for the unsupervised group (70.3%) is still significantly higher than the reoffending rate for the supervised group (65.7%). http://www.aic.gov.au/publications/current%20series/tandi/481-500/tandi485.html
You got me quite intrigued about going the negative way but the statistics show otherwise
Crime rates have actually been quite stable and are not on the rise.
But the rate of recidivism (reoffending) is unacceptably high - it's always the same group of people, particularly of indigenous, marginalised, alcoholic origins - and perhaps you can look at the role of the parole board in rehabilitating those who have been released.
I mean you could always argue, using the statistic you have just cited, that since it's always the same type of people going into jail (and the cycle repeating itself), you could perhaps look at how sentencing works in addressing all this. Another question you should look at is: Is the Parole Board being overworked? I mean, it's probably not their fault that the board only meet up once a month (or something like that) and only spend 15 minutes on each applicant -> does this lead to reoffending? Perhaps it's more of an issue of funding and bureaucracy than the Parole Board failing in its duty per se?
I also have to agree with Professor Polonsky that crime is often hyped up by the media. Levels of crime have not risen (sometimes even falling) and, in my opinion, it is exactly this reason that people think it's getting worse (and leading to cries of things like the PB failing). Because crime (the most serious ones) are getting rarer, its occurrence begs for more attention than it would if crime occurred more often. So perhaps, you could zoom out, and argue that really the Parole Board hasn't failed, it's just that a few sensationalised cases (Jill Meagher etc) have created such perceptions. (again, you can argue the opposing side as well)
Other things you can look at (with regards to parole board)
*How the media chooses to victimise people. ("The ideal victim") -> How does this affect how the parole board operates?
*Broken Windows theory (i.e. fixing the environment in which criminal activity occurs)
* Principle of parsimony (what PP mentioned: how prison sentences should only be given at as a last resort, and only enough to address the crime -> should we be giving harsher sentences? Can this alleviate the shortcomings of the Parole Board?)
And I also like how you are thinking of exploring rehabilitation vs punishment - it's really interesting actually!