What systems are in place to ensure that the convict has actually changed and won't commit the offence again?

Many systems have been set up to do just that. While in jail, prisoners get the chance to study and re-educate themselves, there are instances that search for work for them when they get out, a whole social service is there...
Most of them don't take these offers though. They just do their (too short) time, get out and very often restart where they left off before they were caught... (of course not all do this, but the one's that do represent a substantial amount)
I must say that when I started my job I thought that every human was essentially good, and when they go "bad", something had happened to them along the way which made them act the way they acted.
Now my vision has changed : I still believe most people are essentially good, but some really are evil and incorrigible. Those individuals should be dealt with and never be alowed to set one foot in the free society since they are a menace to all other individuals.

I know it's not very PC to say this, but I'm going to say it anyway. I think the "soft" approach used over the last 20 years has failed and at best only contributed to the problem. I have the feeling authorities get softer on criminals every year, and this while crime rates skyrocket and get higher every year.

What should be done then? I really believe additional funds should be released for every stage of the juridical system. (from the police officer that catches them to the judge that convicts them to the prisons they are put away in) This money should be invested in MORE people and MORE and BETTER means to work with. So that once again criminal investigation could be thorough again instead of half-assed because it all "costs too much". Because that's the real problem : the cost. That's why the soft approach is more popular with most governments : it costs less because with that approach they don't have to invest as much in people and means. They want to make the general public believe that what is lacking in people and means will be compensated by the social factor. It isn't, and it's really pernicious for the quality of the whole legal system. But I have the feeling that the powers that be don't really care about this.

I'm sorry to hear this about your family member, but this only adds to my point : with more means and more better skilled people we would be able to put the RIGHT people behind bars for a LONGER period of time.