Marie Black, 34, convicted of offences including rape and inciting a child to engage in sexual activity, with two men guilty of similar charges

A woman at the centre of a paedophile ring which set children up as “sexual playthings” over more than a decade has been found guilty of offences including rape, conspiracy to rape and inciting a child to engage in sexual activity.

Ten people – six women and four men – had been on trial accused of the abuse of five children. Marie Black, from Norwich, was alleged to have been at the centre of the abuse.

Black, 34, denied 26 charges during a three-month trial at Norwich crown court, but on Monday the jury convicted her on all but three counts after 19 hours of deliberations. She sobbed uncontrollably in the dock as the verdicts were delivered and was heard saying: “I’ve been stitched up.”

Michael Rogers, 53, of Romford in Essex, was found guilty on 14 counts including cruelty, rape and inciting a child to engage in sexual activity. Jason Adams, 43, from Norwich, was found guilty on 13 similar counts.

Judge Nicholas Coleman remanded all three in custody until sentencing on 28 September, saying: “These are very serious matters.”

Facebook Twitter Pinterest Michael Rogers and Jason Adams. Photograph: Norfolk Constabulary/PA

Carol Stadler, 59, from Norwich, was found guilty of assault causing actual bodily harm but cleared of nine other charges, including serious sexual assaults, and was released on bail. The remaining defendants – Anthony Stadler, 63, Nicola Collins, 36, Andrew Collins, 52, Judith Fuller, 31, Denise Barnes, 43, and Kathleen Adams, 85, all from Norwich – were cleared on all counts.

Opening the trial, prosecutor Angela Rafferty QC had said Black, previously known as Marie Adams, played an instrumental role in using the children as “sexual playthings”. The abuse, which is said to have happened in and around Norwich and London, included forcing the children to have sex with one another.

On some occasions, the adults threw parties and played card games to decide who would abuse which child, Rafferty said. In interviews the victims described how they were abused in front of one another and other adults. Some of the abuse involved children’s toys, including Barbie dolls.

They said the abuse became so routine that the victims came to accept it as normal. One of the male victims said: “There would be parties and they would do some games where the boys were in one room with the men and the girls were in another with the women. The adults would have a card game and the winner would get to choose a boy to start touching their private parts and then hurt them afterwards.”

Describing Black, Rafferty said: “Was she a helpless victim of abusive males or was she herself deeply involved with the children’s ill treatment?”

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She added: “Many of the defendants have become good at appearing normal and respectable. This is what you would have to do in order to be child abusers to the extent alleged here.”

All of the defendants denied abusing the children, saying it simply did not happen. During the trial it emerged that police had launched an investigation into the conduct of Norfolk county council social workers involved in the case.

The court heard the trial had been due to start last year but was delayed when prosecutors raised concerns over changes made by social workers to statements taken from the children which resulted in Norfolk police launching an investigation into alleged misconduct.

Sarah Elliott QC, representing Black, told the court that at the time the county’s children’s services department had recently failed an Ofsted inspection, being ranked “inadequate” in all areas.