A 17-year-old boy who started a fire in a sheltered housing complex in Rugby has been sentenced to a hospital order.
The teenager, who cannot be identified for legal reasons, pleaded guilty to setting fire to a mobility scooter in Harold Cox Place on 1 March 2010.
No-one was hurt, but he was charged with two counts of arson being reckless as to whether life was endangered.
The jury at Birmingham Crown Court was directed to enter a not guilty verdict on two further counts of arson.
Nigel Reader, from West Midlands Crown Prosecution Service, said it had been a complex case.
"Not least because of all the competing interests involved, namely a number of young and vulnerable witnesses and a young defendant who has learning difficulties," he said.
The youth will now be detained under section 37 of the 1983 Mental Health Act.
He had previously been cleared of causing an earlier fire at the sheltered housing complex, which resulted in the deaths of a husband and wife from Rugby.
Kathleen Mabel and Albert Adams, both aged 77, died several hours after a mobility scooter fire spread to their home on 27 February 2010.
A trial judge at Birmingham Crown Court ordered jurors in February 2011 to return a not guilty verdict for a charge of arson with intent to endanger life.
He also said an outstanding charge of manslaughter relating to Mr and Mrs Adams' deaths should remain on the file.
The family of Mr and Mrs Adams said they were "very disappointed" with the outcome of the trial.
In a statement released through Warwickshire Police they said: "The person who was originally arrested for our parents' manslaughter was let off that charge if he pleaded guilty to the lesser crime of the second fire.
"We feel very let down by the justice system.
"No justice has been given to our extended family or to our wonderful mum and dad."
Paying tribute to the couple they said: "They would help people wherever they could and are missed by everyone but especially by their grandchildren."
They added: "The British justice system failed them and us.
"Our family are still struggling to come to terms with mum and dad's horrific and needless death."