"Prosecutor Paul Sloan QC told the jury at Newcastle Crown Court that Mr Agis was guilty of manslaughter by gross negligence.
He said the artist was "well aware" of the dangers that strong gusts of wind posed to Dreamspace.
The sculpture was set up on 18 July by Mr Agis and event organisers Brouhaha International, and secured by ropes attached to metal pegs hammered into the ground.
On 23 July, the day of the incident, an employee of Brouhaha reported to Mr Agis that the left-hand side of the structure had lifted up while she was inside it.
Another employee later noticed that the wind was getting underneath and lifting it up several feet.
Mr Sloan said that the normal procedure in such a case was to evacuate the structure immediately, and an evacuation began.
But Mr Agis, having taken a look, said that it was all right for members of the public to re-enter.
"He did, however, instruct two Brouhaha International employees to attach some more ropes to pegs around the structure," Mr Sloan said.
"They put some extra ropes at the front, to the left of the entrance, and along the left-hand side of the structure.
"They were then interrupted by the defendant, Maurice Agis, who told them to resume duties at the entrance dealing with members of the public, so that he and his partner could enjoy a refreshment break.
"
well that's what would seal it for me as far as him being justifiably prosecuted (not guilty mind but enough information to warrant a trial)
he was part of the construction team. he was aware of or reckless with regards to the dangers of a gust of wind. he was informed of a danger with regards to the structure and assumed the responsibility of declaring it safe for re-entry when perhaps he should not have. and then he interrupted the necessary safety procedures on his own authority.
as i said i don't know if he's guilty or not, but i can see why he could be viewed as criminally liable