They accused Yoon of showing “no remorse” for actions which threatened “constitutional order and democracy”.
“The greatest victims of the insurrection in this case are the people of this country,” they said.
“There are no mitigating circumstances to be considered in sentencing, and instead a severe punishment must be imposed.”
Speaking in his own defence, Yoon was defiant, saying he was simply exercising his lawful authority as president.
“It was not a military dictatorship that suppresses citizens, but an effort to safeguard freedom and sovereignty, and revive the constitutional order,” Yoon said, as reported by the Yonhap news agency.
The court is expected to hand down its ruling in the case on February 19, Yonhap reported.
Yoon’s defence team compared the disgraced former leader to historical figures such as Italian scholars Galileo Galilei and Giordano Bruno, who were wrongfully condemned.
“The majority does not always reveal the truth,” they said.
Prosecutors also asked that former Defence Minister Kim Yong-hyun be sentenced to life imprisonment.
Proceedings were expected to wrap up last week, but were postponed after 15 hours of deliberation – it took eight hours to examine evidence for Kim alone.
The current trial features eight defendants seen as ringleaders of the martial law bid, including Yoon and Kim.
If found guilty, Yoon will become the third South Korean president convicted for insurrection, alongside two military leaders in connection with a 1979 coup.
Even if he is convicted and sentenced to death, it is highly unlikely that it would be carried out as South Korea has had an unofficial moratorium on executions since 1997.
Prosecutors are also seeking a 10-year prison term for Yoon on obstruction of justice charges, with a Seoul court expected to deliver a verdict in that case this week.
And he faces a trial on charges of aiding the enemy over allegations he ordered drone flights over North Korea to strengthen his effort to declare martial law.
- Agencies France-Presse