Question: Who was the murderer in the first broadchurch?

Disambiguated questions and answers:
context: Actor Matthew Gravelle (who played murderer Joe Miller) was the second cast member to learn the killer's identity. Chibnall called to tell him two weeks before the final three scripts filmed. By this time, Gravelle was already on the set of another television production. Chibnall kept his revelation short, saying, "It's you." Gravelle paused for about 20 seconds, and then said, "Oh, brilllllliant." He was very enthused to be able to play what were going to be critical scenes at the end of the series. But he also admitted he had never guessed he was going to be the killer. Over the next few days, Chibnall and Gravelle had many long conversations to discuss Joe Miller's backstory and motivation, how to integrate the filmed performance with the upcoming performance, and how Gravelle could play the character going forward.
question: Which character was the murderer in the first broadchurch?
short_answers: Joe

Joe Miller
wikipage: Broadchurch (series 1)

context: Actor Matthew Gravelle (who played murderer Joe Miller) was the second cast member to learn the killer's identity. Chibnall called to tell him two weeks before the final three scripts filmed. By this time, Gravelle was already on the set of another television production. Chibnall kept his revelation short, saying, "It's you." Gravelle paused for about 20 seconds, and then said, "Oh, brilllllliant." He was very enthused to be able to play what were going to be critical scenes at the end of the series. But he also admitted he had never guessed he was going to be the killer. Over the next few days, Chibnall and Gravelle had many long conversations to discuss Joe Miller's backstory and motivation, how to integrate the filmed performance with the upcoming performance, and how Gravelle could play the character going forward.
question: Which actor was the murderer in the first broadchurch?
short_answers: Matthew Gravelle

Matthew Ian Gravelle
wikipage: Broadchurch (series 1)

Long answers:
knowledge: content: Broadchurch is a British crime drama television series broadcast on ITV for three series between 2013 and 2017.
wikipage: Broadchurch
long_answer: In the British crime drama television series Broadchurch, the character Joe Miller, played by Matthew Gravelle, was the murderer in the first series. 

knowledge: content: The first series of the British crime drama Broadchurch originally aired on the ITV broadcast network in the United Kingdom from 4 March 2013 to 22 April 2013.
wikipage: Broadchurch (series 1)

content: Although Chibnall had determined who the murderer was by the time casting began, those who auditioned for the program were not told the killer's identity.[35]
wikipage: Broadchurch (series 1) Casting
long_answer: The first series of the British crime drama Broadchurch originally aired on the ITV broadcast network in the United Kingdom from 4 March 2013 to 22 April 2013. Although  the murderer was determined by the time casting began, those who auditioned for the program were not told the killer's identity. Actor Matthew Gravelle, who played murderer Joe Miller, was the second cast member to learn the killer's identity.