Prosecutors will ask the judge in her criminal trial to throw the book at Lindsay Lohan and give her 240 days in jail if shes convicted of lying to cops in her June car accident case.

Sources say that the L.A. City Attorney will be in court, lying in wait in the event Lindsay is convicted.  If the jury finds her guilty, L.A. prosecutors will ask the judge to jail her because she would have squarely violated her probation in the jewelry heist case by breaking the law.

L.A. prosecutors will ask for the maximum - 240 days in jail.  Law enforcement sources say that if the judge sentences Lindsay to the max, based on the current formula and the fact that shes a repeat probation violator, Lindsay would actually serve between 60 and 90 days.

The problem being if Lindsay is convicted, shed be placed on probation for another 2 years, meaning if she violates any law, she could be hauled into court again, and possibly serve ever more jail time.