KIBUNGO, Rwanda (AP) _ A former hospital aide in a pink prison uniform became the first person to be tried in connection with Rwanda's 1994 bloodbath Friday. To the jeers of hundreds of spectators, he denied witnesses' accounts of his participation in the slaughter.

Deo Bizimana is accused of killing 20 people and ordering the massacres of thousands more in the genocide orchestrated by the country's former Hutu-led government. Half a million people were killed, most of them ethnic Tutsis.

Efforts to rebuild the country's crippled justice system and craft legislation to prosecute 85,000 suspects took two and a half years. Testimony in Bizimana's trial took four and a half hours.

About 500 people attended the trial in a makeshift courtroom in Kibungo, about 40 miles southeast of the capital, Kigali. They cheered when the judges entered, and jeered the defendant, who now awaits a verdict.

One by one, seven witnesses made brief statements to the three-judge panel.

``Bizimana broke into my house and killed my family, and he thought he had killed me,'' said Eugene Ndongozi, who bore machete scars on his head. ``I used to be a rich man, but now I have nothing.''

The defendant responded: ``If he really saw me and I saw him, then I would have killed him, so it is not true.''

One of 1,946 people the current Tutsi-led government considers to have led and organized the massacres, Bizimana could get the death penalty and cannot plea-bargain.

More than 85,000 others are crammed into Rwandan prisons awaiting trial for lesser genocide-related crimes. More trials are expected to begin throughout Rwanda on Monday.

The Rwandan government trials are seen as crucial to ending the cycle of impunity that allowed politically motivated slayings of both Tutsis and Hutus to go unpunished for generations, setting the stage for the 1994 genocide.

Rwandan officials say that once the organizers of the genocide are convicted and executed, it will be easier to show leniency for those who followed their orders, promoting reconciliation.

Bizimana was charged with 11 crimes ranging from organizing a genocide to unlawfully discharging an assault rifle and a grenade.

``We are going to judge this man for killing many people,'' prosecutor Jean Rugerintwaza said in his opening statement. ``He is known all over Rwanda as a killer and for being well-liked by the former government for giving guns to the people and teaching them to kill Tutsis.''

He called for the death penalty.

Bizimana insisted the witnesses and the prosecutor had conspired against him and had obtained a handwritten confession through torture, but couldn't produce any evidence when a judge asked him to.

He said he had only been a member of the ruling party that organized the genocide, not a participant in it.

``They have no detailed information about what they say I did,'' said Bizimana, who represented himself because no attorney could be found to defend him.

The U.N.-appointed International Criminal Tribunal for Rwanda, based in Arusha, Tanzania, has indicted 21 people on charges connected with the slaughter, but has been sluggish in prosecuting them.

The government aborted an attempt to begin trials in April 1995 after just one day when it became clear it was logistically and legally unprepared to do so.

Following the genocide and subsequent flight of 20 percent of Rwanda's mostly Hutu population to neighboring countries, only 50 attorneys remained and most court facilities were destroyed.

Foreign donors have since spent millions of dollars trying to help the government rebuild the shattered justice system and parliament passed special genocide legislation in August 1996.

Ministry of Justice officials had pledged to the international community that trials would begin in 1996.

Egide Gatanaza, another accused genocide organizer in the Kibungo area, took the stand Friday after Bizimana. A former local leader, Gatanaza is charged with leading massacres, training militias of young men, or Interahamwe, who carried out many of the killings, and rape.

Human rights groups estimate that more than 15,000 people were killed in the Kibungo area before Tutsi-led rebels captured the region on April 22, 1994, just 15 days after the massacres began.

U.N. human rights monitors and a representative from Human Rights Watch-Africa sat in as observers. Rwandan state television taped the proceedings, which were broadcast live on Radio Rwanda.

As the trial opened, the last of 535,000 Hutu refugees returning from camps in Tanzania walked past the courtroom on their way home. More than 640,000 refugees have returned from Zaire in the past two months.

Officials have arrested at least 2,000 of the returning refugees in connection with the genocide. The Hutus had fled in fear of retribution after the Tutsi-led rebels took power.