Saddam took his seat in the dock on Wednesday after a two-day recess, with his seven co-defendants also in court.
Shortly after the trial resumed, Rauf Abdel Rahman, the chief judge, announced that "the experts verified these documents and the signatures of Saddam Hussein were found to be authentic".
But Abdel Rahman told the prosecution that one document could not be inspected because it was a photocopy and an original was required.
After a session of about three hours, Abdel Rahman adjourned the trial until April 24 to allow experts to look at more documents.
The experts' report did not give details on the documents, but one of them was dated June 16, 1984.
That is the same date of a memo approving the death sentences of the Shia, presented by prosecutors earlier in the six-month-old trial.
On Monday, Abdel Rahman had adjourned the trial after only an hour to allow the prosecution more time to prove that the signatures were those of Saddam and his half-brother, Barzan Ibrahim Hasan al-Tikriti.
Jaafar al-Mussawi, the chief prosecutor, had presented a report by three handwriting experts that he said proved the claims.
Saddam's lawyer, Khalil al-Dulaimi, contested the report, demanding that a neutral body make a judgment on the authenticity of the signatures.
Khamis al-Obaidi, another defence lawyer, said the experts were interior ministry employees "and not neutral. They are against the former regime."
The documents came from the Revolutionary Command Council, the highest decision-making body in Saddam's former government.
In two earlier hearings, Saddam acknowledged that he had ordered the trial of Dujail villagers suspected of plotting to assassinate him, but stopped short of admitting he was responsible for their executions.
After the Dujail trial, Saddam and six others will also face charges of genocide over the 1988 Anfal campaign against Kurds that left as many as 100,000 people dead.