The trial of baby nurse Lucy L., who is charged with the murder of seven babies and attempted murder on 10 other counts, began in Manchester on Tuesday.
The 32-year-old woman, who denied the charges, was videotaped into the courtroom from the detention center.
In the brief opening session, she only confirmed her identity.
L., who comes from Hereford, was first arrested in 2018 after the Chester maternity ward registered an unusual increase in the number of deaths.
The baby nurse is believed to have murdered five boys and two girls over the years she worked at the Countess of Chester Hospital in Chester, north-west England.
Between March 2015 and June 2016 she is said to have tried to kill another five boys and five girls.
The ages of the victims and their identities have not been released by the court.
The court also barred journalists from publicly identifying the victims' parents and other witnesses.
Other backgrounds are also unknown.
The process will probably take six months.