Evren, 94, and another coup plotter, went on trial this week in a landmark case in the decades-old tussle for supremacy between elected politicians and Turkey's army.
But both Evren and former air force commander Tahsin Şahinkaya, 87, failed to appear in the Ankara court on the first day of their trial on Wednesday, and again on Thursday, citing ill health.
It is only in the last 10 years that the power of Turkey's military "Pashas" has been gradually reined in as part of democratic reforms by Prime Minister Recep Tayyip Erdoğan's government aimed at bringing Turkey closer to European Union membership.
"According to the constitution, every citizen is equal before the courts and every Turkish citizen is to be tried before Turkey's courts," lawyer Ural Gündogan, who represents a number of leftist coup victims, told the court.
Evren and Sahinkaya must be brought before the court, he said "to make them understand the equality article of the constitution ... and by force if necessary."
Evren and Şahinkaya should be treated no differently to former Egyptian President Hosni Mubarak and Chilean dictator General Augusto Pinochet who were both forced to appear in court despite their advanced age and ill health, lawyers said.
"Just as Hosni Mubarak was brought to court and questioned in a cage and Pinochet was brought in a wheelchair, Evren should be brought in on a hospital bed if necessary. Evren was no less of a dictator than them," Sabah newspaper quoted lawyer Celahattin Can as saying.
The panel of three judges demanded medical reports for the two defendants and said they would rule whether the indictment could be read in their absence.
In the meantime the court heard statements from victims seeking to be co-plaintiffs in the case so their grievances are taken into account during the prosecution and possible sentencing phase of the trial.
One of them, grey-haired, thin and bespectacled Mustafa Yalçıner, was head of Revolutionary Communist Party before the 1980 coup.
"I was arrested after the coup and tortured for months," he told the court. "Evren and Şahinkaya should be charged with being public enemies and treason."
Turkey remains haunted by those times, when virtually the entire political class was rounded up and interned. Hundreds died in jail, and many more disappeared in three years of military rule after the coup, Turkey's third in 20 years.
Tanks were posted at strategic points across Turkey's cities and troops roamed the streets enforcing martial law.
Turkish President Abdullah Gül said the trial should serve as a warning to others.