OAKLAND, Calif. -- A judge's ruling that former BART police officer Johannes Mehserle be ordered to stand trial on murder charges for the shooting death of Oscar Grant III should be thrown out because it was "irrational," Mehserle's attorney alleges in a motion to be discussed in court Friday.

Defense attorney Michael Rains, in a motion to dismiss the charges against Mehserle that he filed in Alameda County Superior Court on July 14, also claimed that Judge C. Don Clay was biased against Mehserle during a seven-day-long preliminary hearing that concluded on June 4 because of "external pressures."

Mehserle, 27, shot Grant, a 22-year-old Hayward man, once in the back with his service weapon on the platform of the Fruitvale BART station in Oakland shortly after 2 a.m. on Jan. 1 after he and other officers were called to the station in response to reports of a fight on a train.

Rains admitted during the preliminary hearing that Mehserle killed Grant but claimed that it was "a tragic accident" because Mehserle meant to use his Taser gun on Grant and fired his gun by mistake.

Rains said Mehserle shouldn't face murder charges because there's no evidence that he exhibited malice during the short, two-and-a-half-minute time period he was on the station's platform before the shooting. He said Mehserle should face a lesser charge such as manslaughter.

But at the end of the hearing Clay said, "There is no doubt in my mind that Mr. Mehserle intended to shoot Oscar Grant with a gun, not a Taser."

Although Rains and prosecutor David Stein were scheduled to appear in Judge Thomas Reardon's courtroom Friday in connection with the motion to dismiss, court officials said a hearing on the merits of the motion will be postponed because prosecutors weren't served the motion in a timely manner and need time to prepare their response.

Court officials also said Mehserle, who remains free in lieu of $3 million bail, won't appear in court today because the hearing will only focus on scheduling matters and is only expected to take a few minutes.