Thanks for the feedback.
I'd like to explain all this in the logline but how?
>>> Does it mean they live out their shortened lifespans in prison? And what's the rationale for this drawn out punishment rather than quick and dirty capital punishment?
In our world you can be sentenced to a certain number of years in prison, but it's very much expensive, so in the future some prisoners can convert their sentence to instant aging, for example a sentence of 45 years of prison can be converted to an aging of +45 years. The main character is 18, he's sentenced to 45 years, plus 2 weeks of a ridiculous "educational program", then he's free but he's 63 y old. The conversion can be also personalized during the trial, for example a life sentence can be converted to 60 years or something like that ? I must research a little to write something ?realistic?. The future society I want to portray is extremely hypocrite; it wants to appear just and fair, so death penalty is totally abolished, but it gives up completely about the idea of the reeducation purpose of the prison.
>>> why should the audience care about
A murderer isn't always a 100% bad person that you want to see in jail for a lifetime, or dead. In the movie we don't see what crimes he has committed at the beginning so I think we can root for him quite easily. The institution is presented like a system who doesn't really cares about re-education and I think we can perceive that in some way the "aging" punishment is not fully fair- the main character was young and chose this punishment because he was scared about the life in prison but he regrets his decision, so when he learn about a 'cure'... besides, he wants to get back to his beautiful girlfriend too.