Mrs Prior KC said items including baby oil, Vaseline and syringes were found, and his stepson notified the police about his concerns.
She said Ruben went on to play the “sweet game” with six boys that night – Saturday 26 July – and they were all ill the following morning.
“The police had not gone out by that stage,” she added.
The police watchdog, the Independent Office for Police Conduct (IOPC), previously told the BBC it was investigating Leicestershire Police’s handling of the incident.
Mrs Prior KC said the children were having difficulty walking due to being ill, so Ruben’s stepson called the police again.
She said Ruben then played the “sweet game” in a room of five children.
Mrs Prior KC said police did then attend, and Ruben was arrested at a nearby pub, where he was having a meal with some of the children.
She said eight of the children were taken to hospital, with five of them being “very ill”.
Devices belonging to Ruben were later analysed and were found to contain more than 50 category A indecent videos of children, which are the most serious kind.
Category B and C videos were also found.