A Superior Court jury in San Diego today found former multimillionaire banker and financier C. Arnholt Smith guilty of state income tax evasion.

Smith, 80, was found innocent of grand theft in the 1974 sale of the San Diego Padres major league baseball team to hamburger chain magnate Ray Kroc. The jury said it had reached an "impasse" on six other counts of state income tax evasion and grand theft.

Judge Robert W. Conyers sent the jurors back for further deliberations.Regardless of the outcome on the other charges, Conyers will sentence Smith, a former San Diego civic leader, philanthropist, Republican Party power, and onetime close friend of former president Richard M. Nixon.

Smith faces a miximum state prison term of five years and a $2,000 fine on the income tax evasion conviction.

Smith has succeeded in avoiding jail since the 1973 collapse of his U.S. National Bank, the nation's 87th largest. If sentenced to jail by Conyers, Smith could remain free for four or five years while the case is appealed.

The jury returned its verdict in its ninth day of deliberations after an eight-month trial-the longest and costliest criminal trial in San Diego County history. Sixty-five witnesses testified in the complicated proceedings, in which 2,000 documents were introduced as evidence.