SAN FRANCISCO (AP) — A federal jury convicted Barry Bonds of a single charge of obstruction of justice Wednesday but failed to reach a verdict on the three counts at the heart of allegations that he knowingly used steroids and human growth hormone and lied to a grand jury about it.

Following a 12-day trial and almost four full days of deliberation, the jury of eight women and four men could reach a unanimous verdict only on one of the four counts against Bonds. U.S. District Judge Susan Illston declared a mistrial on the others, a messy end to a case that put the slugger — and baseball itself — under a cloud of suspicion for more than three years.

Bonds sat stone-faced through the verdict, displaying no emotion. His legal team immediately asked that the guilty verdict be thrown out and Illston did not rule on the request. She set May 20 for a hearing in the case.

The case also represented the culmination of the federal investigation into the Bay Area Laboratory Co-Operative steroids ring. Federal prosecutors and the Justice Department will have to decide whether to retry Bonds on the unresolved counts.

The counts that the jury could not resolve accused of Bonds of lying to the grand jury investigating BALCO in 2003 when he said he never knowingly took steroids or HGH, and when he said he was never injected by anyone except his doctors.

WATCH NBC NIGHTLY NEWS COVERAGE OF THE BONDS VERDICT:

Visit msnbc.com for breaking news, world news, and news about the economy

Each count Bonds was tried on carries a maximum sentence of 10 years in prison. However, federal guidelines suggest a total sentence of 15 to 21 months. For similar offenses in the BALCO case, Illston sentenced cyclist Tammy Thomas to six months of home confinement and track coach Trevor Graham to one year of home confinement.

Bonds walked out of the courthouse with his lawyers, who instructed him not to comment because they said the case isn’t over.

Impeccably dressed in suit and tie, Bonds flashed a victory sign to a few fans.

“Are you celebrating tonight?” one asked.

“There’s nothing to celebrate,” he replied.

Lead defense attorney Allen Ruby said the prosecution failed to prove the heart of its case.

The obstruction of justice count was a complicated charge that asked jurors to decide if Bonds was being evasive when making any one of seven statements to the grand jury. He was convicted on a single statement about his childhood as the son of major leaguer Bobby Bonds and his relationship with personal trainer Greg Anderson — it did not address performance-enhancing drugs.

The government “has determined it’s unlawful for Barry Bonds to tell the grand jury he’s a celebrity child and to talk about his friendship with Greg Anderson,” Ruby said.

Now 46, Bonds set baseball’s career home run record with 762 while playing for the Pittsburgh Pirates and San Francisco Giants from 1986-2007. The jury met less than two miles from the ballpark where the seven-time NL MVP played for his last 15 years.

Bonds was indicted on Nov. 15, 2007, exactly 50 days after taking his final big league swing and 100 after topping Hank Aaron’s career home run mark of 755. He also set the season record with 73 home runs in 2001 with the Giants.

Illston would not let prosecutors present evidence of three alleged positive drug tests by Bonds because Anderson refused to testify and there was no one to confirm the samples came from Bonds.

Bonds acknowledged that he did take steroids but said Anderson misled him into believing they were flaxseed oil and arthritis cream.

Anderson was sentenced by Illston in 2005 to three months in prison and three months in home confinement after pleading guilty to one count of money laundering and one count of steroid distribution. The trainer was jailed on March 22 for the duration of the trial after again refusing to testify against Bonds. He was released last Friday.

Jeff Novitzky, the federal agent who started the BALCO probe, had been hoping the Bonds case would be part of a wider investigation of doping in baseball. Last year, the 9th U.S. Circuit Court of Appeals ruled that Novitzky and his team of investigators illegally seized urine samples and records from 104 players in 2004.

Separately, Novitzky has helped develop the case against former star pitcher Roger Clemens, who is scheduled to stand trial in July for lying to Congress by denying he used performance-enhancing drugs. Novitzky also is a key player in the federal doping investigation of pro cyclists, including seven-time Tour de France winner Lance Armstrong. Rep. Jack Kingston, a Georgia Republican, recently suggested that the federal agent is motivated by a desire to bring down a celebrity.

Copyright 2011 The Associated Press.