The L.A. County District Attorney believes Lindsay Lohan is a seasoned fashion thief, and that's a primary reason why she's being prosecuted for felony grand theft.

D.A. Focuses On Lindsay's Shady Shopping  Sources connected to the case tell us ... in deciding whether to prosecute, the D.A.'s Office heavily considered 3 incidents where Lindsay allegedly pilfered expensive items:

D.A. Focuses On Lindsay's Shady Shopping-- She was suspected of taking a $400,000 necklace in 2009 from an Elle Magazine photo shoot.
D.A. Focuses On Lindsay's Shady Shopping -- She was accused of stealing a $12,000 mink coat in 2008 from a NYC nightclub.

D.A. Focuses On Lindsay's Shady Shopping -- She was accused of taking a $35,000 Rolex from a "friend" in 2010.

D.A. Focuses On Lindsay's Shady Shopping Lindsay was not prosecuted or convicted in the three cases, but sources say prosecutors not only heavily considered the prior incidents in making their decision ... they will ask the judge to admit the 3 incidents into evidence to show  "prior bad acts" if the case goes to trial.

D.A. Focuses On Lindsay's Shady Shopping Our sources say there are two other factors that weighed heavily in the decision to prosecute:

D.A. Focuses On Lindsay's Shady Shopping -- Lindsay has had repeated run-ins with the law, including 2 DUIs.

D.A. Focuses On Lindsay's Shady Shopping -- She repeatedly thumbed her nose at the legal system by failing to perform her probation requirements, blowing off court appearances (remember that trip to Cannes?) and acting disrespectfully before the judge (the whole fingernail thing).

D.A. Focuses On Lindsay's Shady Shopping As TMZ reported, the D.A. has a surveillance video which shows Lindsay walking out of a Venice, CA jewelry store with the $2,500 necklace in question.  The necklace is partially hidden by other trinkets around Lindsay's neck.

Lindsay will be arraigned today at 1:30 PM PT.  Lindsay will be in court, accompanied by her lawyer, Shawn Chapman Holley.  Prosecutor Danette Meyers reps the people of the State of California.