As I imagine it, jail wouldn't be something anyone specifically imposes; it emerges out of the combination of your high estimated risk level and your inability to afford insurance except when confined to a secure facility.

... and we could offer those imprisoned a chance to earn the required money through a system of gladiatorial combat! If you win enough fights and survive the rest then you will have a chance to earn your freedom! Some people may even elect to sell themselves into the system to cover their existing debts and secure their family financially. Good old fashioned capitalism at play!