SAN FRANCISCO (Reuters) - A jury verdict finding baseball home run king Barry Bonds guilty of obstructing justice in a steroids investigation should be thrown out, his attorneys argued in court papers filed on Wednesday.

Bonds was ensnared in a probe by U.S. prosecutors over the use of performance-enhancing drugs in sports. The steroids scandal has tarnished some of the biggest stars in baseball.

A Northern California jury convicted Bonds in April on a single count of obstruction of justice, but deadlocked on three other counts of lying to a grand jury. The government has not announced whether it will seek a retrial on the deadlocked charges.

Bonds' attorney Dennis Riordan argued in a court filing that a judge should order his acquittal on the obstruction count, or set a new trial.

The statements considered obstruction by the jury were not false, Riordan argued, even though the government argued they were evasive and illegal.

"But unauthorized rambling is not a federal crime," Riordan wrote.

The charges stemmed from Bonds' testimony to a 2003 grand jury investigating the Bay Area Laboratory Co-operative, or BALCO.

Testifying to the grand jury, Bonds admitted getting flaxseed oil, vitamins, protein shakes and creams from his trainer, but he said he had no knowledge of human growth hormones or steroids. He said no one ever injected him other than medical doctors.

Bonds was the National League's most valuable player seven times and finished his career in 2007 with 762 home runs, most in the history of Major League Baseball. Bonds, who spent much of his career with the San Francisco Giants, also set the single-season home run record with 73 in 2001.

He was indicted three months after breaking Hank Aaron's career homer record in 2007.

The case in U.S. District Court, Northern District of California is United States of America v. Barry Lamar Bonds, 07-cr-0732.

(Reporting by Dan Levine; Editing by Peter Cooney)