After the investigation is complete, the law enforcement agency may submit a request to the DA that certain charges be filed. The DA will review the reports and evidence and decide what charges that they intend to file. Once the filing decision is made, a criminal complaint is submitted to the court with the filed charges and the case against the defendant is initiated. In cases where the defendant is not in local custody, an arrest warrant declaration is submitted with the complaint. A judge will review the declaration and, if it contains sufficient information, the arrest warrant will issue.
In that process, there are many potential points of delay. However, this is a pretty routine process, once initiated, and is typically fairly efficient. An arrest warrant for this type of crime is typically issued in San Bernardino with 2-4 weeks, but keep in mind that that is a very broad generalization.
Once issued, the warrant will remain in the system essentially forever, until it is affirmatively recalled.
So long as the defendant is an adult, it is possible to check on the court's computer to see if a case has been filed and/or a warrant issued for the case. You may check case status at http://220.127.116.11/openaccess/
All of that said, crimes of domestic violence are taken very seriously in San Bernardino (and California in general). Furthermore, depending on the facts, there are additional serious crimes that may have been alleged here. I strongly urge Boyfriend to consult with an attorney ASAP, so he can figure out his best course of action. If the asker is Girlfriend, she may want to consult an attorney as well, regarding pursuing a restraining order and other potential legal issues.
Any statements I make in these forums (fora?) should not be taken as direct legal advice, merely informed guidance. This is true due to the anonymous nature of this venue, and the incomplete information which is invariably provided by the questions. It is imperative that you consult directly with an attorney regarding your specific situation before acting on or relying on anything represented here. Period.
A warrant may have already been issued. A call to the local sheriff's department warrant's division where the incident occurred can confirm whether there is a warrant. A warrant can expire or renewed so that it is active for many years. Even if it expires, if an individual leaves the state to avoid the warrant, it can become problamatic years later. Better to consult an experienced criminal defense attorney if a warrant has issued. There may be speedy trial issues that can result in a dismissal, but there are various factors and consulting an experienced attorney will give the answers you seek.
There is no set time frame for an arrest warrant. If the girlfriend reported it to the police the police can ask a Judge for an arrest warrant based on the girlfriend's statement. Once an arrest warrant is signed by a Judge it lasts until the person is arrested or dies.
The police can also submit the report to the District Attorney's office. If the DA's Office files charges then an arrest warrant can be issued by a judge if the DA applies for the warrant. That arrest warrant will last until the person is arrested or dies. They do not expire.