The hit BBC police drama returned with its long-awaited sixth series on BBC1 on Sunday, 21 March — World Down Syndrome Day — with the lead suspect in the case being Terry Boyle, played by Tommy Jessop, a character with learning disabilities who Superintendent Ted Hastings called "the local oddball".
The reference came under fire after the show aired, but writer Mercurio has hit back — revealing the quote was taken directly from the Jill Dando murder case.
Mercurio wrote on Twitter: "'I was the easiest target on the case. They (police) could just say, "We’ve got the local oddball".' Direct quote from Barry George.
"'Oddball' has no connotation for learning difficulties. It describes a loner, an eccentric. It’s an equally fitting description for someone like Christopher Jefferies. The drama is using the term to refer to the Dando case, not to learning difficulties.
Watch: Line of Duty Series 6 teaser
"We work with numerous police advisers. Line Of Duty portrays policing with some of its failings. The officer in question doesn’t work with vulnerable people and hadn’t met the suspect. The ones dealing with the suspect used different, more appropriate language...
"I’m not sure if you’re saying no police officer would use that term (some would - and way, way worse, tbh) or that TV drama can’t use a term that, for the reasons I’ve explained, just doesn’t have the intended connotation you’ve subjectively attributed...
".. the main reason being a reference to a real case of police mishandling of a vulnerable suspect."
Barry George was convicted of killing TV presenter Jill Dando in 1999, but was acquitted in 2008.
Mercurio was responding to safeguarding expert Jim Gamble, who was one of many to object to the "oddball" line in the police drama.
He tweeted: "Especially on the day that it is but also on any day, the script writer of #LineOfDuty needs to reflect on the line referring to a suspect with special needs being referred to as the local odd ball."
A BBC spokesman said: "Ted Hastings has never met Terry Boyle. In the scene, he is reviewing the evidence against the character.
“The word used in dialogue refers to an eccentric or loner, which fits the stalker/obsessed fan theory of Gail Vella’s murder. The dialogue has no meaning or connotation that relates to the character’s disability.”
Line Of Duty – which was forced to halt filming due to the outbreak of the coronavirus pandemic in March 2020 – returned to BBC1 on Sunday with Hollywood star Kelly Macdonald joining regular cast members Vicky McClure, Martin Compston and Adrian Dunbar.
The police drama follows police anti-corruption unit AC-12 and the debut episode of the new series saw a record audience of 9.6 million tune in.
Watch: What to watch on NOW TV in March 2021