The judge was alerted after jurors were observed writing vertically, rather than horizontally. It had been assumed they were taking notes.
"Yes, it helps me keep my mind busy paying more attention," the jury foreman told the judge Tuesday. "Some of the evidence is rather drawn out and I find it difficult to maintain my attention the whole time, and that doesn't distract me too much from proceedings."
Jurors in the trial are anonymous, and no action can be taken against them for the puzzle playing.
The foreman admitted to the judge four to five jurors were playing puzzle games for up to half the time the trial had been going.
"Jurors are sort of the judges of the facts and it's very disappointing they weren't giving our clients a fair trial," said Robyn Hakelis, a lawyer for one of the defendants.
A new trial is expected to begin in a few weeks.