Two women accused of murdering the estranged half-brother of Kim Jong-un, the North Korean leader, must have been trained to carry out an assassination using a deadly nerve agent, Malaysian prosecutors have said.

Indonesian Siti Aisyah and Vietnamese Doan Thi Huong are charged with having common intent with four North Korean fugitives to kill Kim Jong-nam at Kuala Lumpur international airport in February 2017.

Kim’s face was smeared with VX, a banned nerve agent developed as a chemical weapon.

“You have to be trained for it – there can be no room for error,” said the prosecutor Wan Shaharuddin Wan Ladin at the high court in Shah Alam on Thursday, likening the killing to something from a James Bond film.

The two women, both in their 20s, are the only suspects in custody and could face the death penalty if convicted. They have pleaded not guilty, saying they believed they were acting in a prank reality show and did not know they were handling anything lethal.

Wan Shaharuddin said assassins would have had to know the best route for VX to enter the victim’s body and know that they must wash the nerve agent off themselves within 15 minutes to avoid being contaminated.

Airport security footage screened in court showed both women heading to a bathroom shortly after the assault on Kim.

“If it was a prank, why did you smear not only on his face or on his eyelids but also in the eye itself?” Wan Shaharuddin said, adding that there was “an element of aggressiveness” involved.

Facebook Twitter Pinterest Siti Aisyah (right) leaves court. The two women could face the death penalty if convicted. Photograph: Vincent Thian/AP

The prosecution made its closing arguments based on the testimony of 34 witnesses in the case. The trial judge, Azmi Ariffin, will make a ruling on 16 August on whether to acquit the women or call for them to enter their defence.

Defence lawyers say the killing was politically motivated, with many key suspects linked to the North Korean embassy in Kuala Lumpur, suggesting the women were pawns. Pyongyang has denied accusations by South Korean and US officials that it was behind the killing.

Kim Jong-nam had criticised his family’s dynastic rule of North Korea, and his half-brother had issued a standing order for his execution, some South Korean politicians have said.

Lawyers for both women said prosecutors had erred in charging them, along with four men seen fleeing Malaysia on the day of the killing, given that several other North Korean suspects had been named during the trial.

“How can there be a common intention between the accused and the four when many others have escaped? There are other suspects who are still at large,” said Gooi Soon Seng, Siti Aisyah’s lawyer.

He described the prosecution’s evidence against his client as “flimsy and circumstantial” as it relied only on security footage and traces of VX byproducts found on a grey sleeveless shirt matching one she was seen wearing at the airport. There was no clear footage showing Siti Aisyah smearing Kim’s face.

The recordings show only a blurry image of someone the prosecution identified as Siti Aisyah hurrying away from the scene. Siti Aisyah’s DNA was not found on the shirt recovered by police, and the VX byproducts detected were commonly found in other substances, Gooi said.

Huong’s lawyer, Naran Singh, said that although his client was seen walking quickly to the bathroom after the killing, she did not seem to have known that her hands were covered in poison. “If someone knew the substance on their hands could kill and that they need to wash it quickly, they would run for their life, not walk,” he said.