FACTBOX - Legal procedure in SocGen fraud case

(Reuters) - French police on Saturday questioned Jerome Kerviel, the 31-year-old dealer blamed for building up huge illicit trades at Societe Generale that cost the bank some $7 billion (3.6 billion pounds) to unwind.

The legal investigation could be long and complex. Here are some of the issues:

CUSTODY

Kerviel was taken into custody at the headquarters of the French finance police early Saturday afternoon.

He can be held for an initial 24 hours of questioning. Prosecutors can then ask for an additional 24 hours at which point they must decide whether to put him under official investigation, opening the way for potential charges, or else release him without pressing any charges.

While he is in custody he will be questioned without a lawyer present.

If he is placed under official investigation, magistrates could decide to continue to arrest him, or else free him under judicial control pending further inquiries.

POSSIBLE CHARGES

Societe Generale has filed a complaint against Kerviel based on three main charges -- fraudulent falsification of banking records, use of these fraudulent records and computer fraud.