I agree that reducing the sentence for a guilty plea could have benefits of more convictions, not fewer. However, I thought it was already the case that judges could impose longer sentences on people who pleaded innocent and were found guilty. So I'm not sure what's different about this proposal, apart from the shorter sentence ...
There was another case recently (not rape, but still a violent assault) which highlighted the use of the Home Detention Curfew (
http://www.bournemouthecho....frenzied_attack__reeased_after_ten_weeks):
>> A Prison Services spokesman said: “We taken the safety of the public extremely seriously. A home detention curfew is available to low risk prisoners serving sentences of more than three months and less than four years, who are deemed appropriate for early release. “To be placed on HDC, a prisoner must have served a quarter of their sentence and spent a minimum of 30 days in prison.”
So if somebody was going to get six years for rape (i.e. longer than average), had it halved to three years, then qualified for HDC, they could be out in only nine months. That mustn't be allowed to happen ...