The remains of retired nurse Judith Fox, 65, were found in woodland next to the River Severn, off The Lloyds at Coalport, near Ironbridge in July last year.
Lucy Fox, 38, of Bernard’s Hill, Bridgnorth, is charged with murder and with arson with intent to endanger life.
Her mother, known as Judy, went missing from her Shifnal home the previous month.
Judge Kristina Montgomery QC told the hearing that Lucy Fox was not present at court in person and would not be appearing via prison video, but that this may change during the course of the trial if the defendant chose to.
"Some of the features of these proceedings are unusual. Among these is that the defendant is absent," the judge said.
"Through no fault of her own she is not fit to stand trial. The court has decided that she is not fit to participate in this trial in any meaningful way."
The jury was sent home shortly after being sworn in at Stafford Crown Court on Monday.
Mrs Fox worked as a staff nurse at the Shropshire Star and Express & Star for 13 years.
Her family released a tribute to Mrs Fox describing her as "a wonderful mother and a devoted grandmother".
The trial continues.