Indonesian prosecutors have called for an Australian resident accused of murdering her friend with a cyanide-laced coffee to be jailed for 20 years.

Jessica Wongso, 27, allegedly poisoned her friend Mirna Salihin at a restaurant in Jakarta in January after ordering her a Vietnamese iced coffee and lacing it with cyanide.

Wongso, whose highly publicised trial has lasted four months, has denied poisoning her friend with whom she studied with at the Sydney design school Billy Blue.

Indonesian prosecutors have called for an Australian resident Jessica Wongso to be jailed for 20 years after she was accused of murdering her friend with a cyanide-laced coffee

Prosecutors allege Wongso sought to 'avenge her pain' over a break-up with her Australian boyfriend Patrick O'Connor, whom Mirna did not approve of.

Her alleged crime was described by prosecutors in the Central Jakarta District Court on Wednesday as 'cruel' and 'sadistic'.

'The defendant's planning to take the life of victim, Wayan Mirna Salihin, was well prepared and showed the defendant's determination,' prosecutors said.

'The defendant's actions were very cruel because it was committed against her own friend.

'(It) was sadistic because the poison cyanide used to take the life of victim, Wayan Mirna Salihin, didn't immediately kill her, but tortured (her).'

CCTV footage from inside the restaurant showed Mirna taking a sip of the coffee before her head rolled back and she began frothing at the mouth moments later.

She died in hospital hours later.

Jessica Wongso, 27, allegedly poisoned her friend Mirna Salihin at a restaurant in Jakarta in January after ordering her a Vietnamese iced coffee and lacing it with cyanide

Her alleged crime was described by prosecutors in the Central Jakarta District Court on Wednesday as 'cruel' and 'sadistic'

Wongso, whose highly publicised trial has lasted four months, has denied poisoning her friend with whom she studied with at the Sydney design school Billy Blue

During the marathon hearing, prosecutors did not give a definitive answer as to where Wongso obtained the cyanide that allegedly killed her friend, arguing instead that it was 'easily available on the black market'

They also took aim at witnesses put forward by the defence, including Australian toxicologist Professor Beng Beng Ong who had told the court the level of cyanide found in Mirna's stomach was not consistent with fatal poisoning and an autopsy was needed.

His evidence should be dismissed, prosecutors said, as he was later detained at the airport and deported for testifying in court on a tourist visa.

While the charge of premeditated murder in Indonesia carries the maximum penalty of death, the Australian Federal Police only agreed to assist the investigation on the proviso such a sentence would not be sought or imposed.

Wongso's legal team are expected to respond next week.

Wayan Mirna Salihin (pictured) died on January 6 after sipping a Vietnamese iced coffee ordered by Ms Wongso

Ms Wongso (left) and Ms Salihin (right) studied together at Billy Blue College of Design in Sydney