(Adds details, background)
By Mike McDonald
GUATEMALA CITY, April 18 (Reuters) - A session in the genocide trial of former Guatemalan dictator Efrain Rios Montt ended abruptly on Thursday, as his lawyers tried to suspend proceedings over a legal technicality and stormed out, leaving him sitting alone in court.
Rios Montt, who ruled between 1982-83, was ordered to trial for genocide and crimes against humanity in January to answer for a counterinsurgency plan that killed more than 1,700 members of the Ixil indigenous group during Guatemala's long civil war.
The 86-year-old's lawyers contend that the judge who ordered the trial should not have presided over pre-trial hearings, but rather another judge, and are seeking to annul the proceedings.
"The debate must return to the (pre-trial) phase," defense lawyer Cesar Calderon said before walking out of the court. "We can't have two judicial processes at the same time. This trial must be annulled."
That left Rios Montt sitting alone in the courtroom without legal counsel. He tried to reach his lawyers by telephone, but got no answer. Judge Yasmin Barrios suggested he appoint a public defender, before calling off the day's hearing and ordering both sides to reconvene on Friday.
Prosecutors dismissed the walkout by Rios Montt's lawyers.
"It's all a political show," attorney Hector Reyes told reporters. "What the defense team is showing is that they have no legal arguments to defend their client and that they have no way to prove his innocence."
Prosecutors allege that Rios Montt, an army general before becoming head of a junta that ruled Guatemala, turned a blind eye during the country's civil war as soldiers used rape, torture and arson to rid Guatemala of leftist insurgents during the 1960-1996 civil war.
His defense team has argued Rios Montt had no control over battlefield operations and that genocide did not take place.
Barrios, who has presided over the trial with two other judges, said pre-trial proceedings should not be repeated and that evidence that was rejected during those initial hearings was reincorporated by her court during the trial.
"This court reiterates it has not violated any proceeding," she said. "The defense's evidence that was rejected can be reincorporated in this process ... which we have done. Returning the judicial process to previous phases would be illegal."
Judge Patricia Flores, who originally charged Rios Montt with genocide and war crimes in January 2012, was recused from the process by defense attorneys last year and judge Miguel Angel Galvez took over pre-trial proceedings.
An appeals court later rejected the recusal of Flores and the defense team has said that she should be the judge to receive evidence instead of Galvez. (Editing by Simon Gardner, Philip Barbara and Christopher Wilson)