If you are a victim of crime and have suffered economic loss such as having unpaid medical bills, you are entitled to "restitution" (or re-payment) for the loss casued by the criminal defendant as part of his/her sentencing upon conviction. This is not a civil suit where you have to "sue" the person and prove a case. Rather, as a crime victim, you are entitled to compensation as a constitutional "right."
California Constitution, Article 1, section 28, subdivision b states, in relevant part: "all persons who suffer losses as a result of criminal activity shall have the right to restitution from the persons convicted of the crimes for losses they suffer."
In addition, California Penal Code section 1202.4 states, in relevant part: "a victim of crime who incurs any economic loss as a result of the commision of a crime shall receive restitution directly from any defendant convicted of that crime. ... this order shall be enforceable as if it were a civil judgment."
So how do you enforce your rights? If you were not already contacted by the prosecutor and know that the defendant is being charged, go ahead and call the local prosecutors office (sometimes called the District Attorney or City Attorney) and ask to speak with the VICTIM WITNESS OFFICE. They will generally send you a form to fill out and will need written proof, such as medical bills, to support your request. Once it is evaluated, the criminal defendant has a right to a hearing to contest the amount you seek. Eventually, if the loss can be proved, the court will order that the defendant make periodic payments to you based upon his/her ability to pay, during the length of probation. If the defendant was sentenced to prison, you are still entitled to restitution. Once you obtain the order, you can use the same, and in some cases additional methods, to collect on the judgment such as placing a lien on the person's property. If the defendant stops paying while he or she is still on probation, be sure to contact the prosecutor's office and let them know immediately.
In addition, if you were a victim of violent crime, there may be funds available through the victim compensation fund. http://www.vcgcb.ca.gov/victims/