If you're not familiar with Sudoku, well, you're probably a new reader of Now I Know -- I've talked about it a number of times over the last few years. But to sum it up, it's a very simple puzzle game. You are presented with a 9x9 grid that is divided into nine rows, columns, and 3x3 subgrids. Some of the squares have one of the digits one through nine already placed in the grid; your job is to fill the rest of the grid up, such that each of the numbers one through nine appears exactly once in each row, column, and subgrid. Here's a blank example board, via Wikipedia, and here's the solution, if you're so interested. 

The game has been around for at least forty years but really got its start in the 1990s when a judge in Hong Kong named Wayne Gould created a computer program that created randomized Sudoku grids at scale. In 2004, he convinced The Times in Britain to include a Sudoku board along with its daily crossword puzzle, and the game took off from there. Other publications in the UK picked up on the trend within a year or so and the impact was measurable; in 2006, the Independent of London (via the Chicago Tribune) reported that pencil sales jumped 700% after the game debuted in the country.

And two years after that, it cost the legal system in Australia about a million dollars.

In the spring and summer of 2008, two Australian men were on trial for allegedly participating in a conspiracy to manufacture illegal drugs. Their trial was a long one -- more than three months. But 66 days in, one of the accused men took the stand. And he noticed something was amiss. Jurors were expected to take notes -- you hear a lot of evidence over ten weeks, and can't be expected to remember everything -- but, per the Sydney Morning Herald, "he saw the jury forewoman playing what he thought was Sudoku." Judge Peter Zahra, according to the Associated Press, had similarly noticed that at least one of the jurors "were writing vertically, rather than horizontally." The defendants, believing they were afforded the full attention of the people who could send them to prison for life, asked the judge to investigate. And it turned out that the Sudoku craze had taken over the jury box.

The judge asked the jury forewoman whether she had been solving number puzzles during the defendant's testimony and she admitted that she had -- and it wasn't just her, and it wasn't just then. Per the Morning Herald, "she said four or five jurors had brought in the Sudoku sheets and photocopied them to play during the trial and then compare their results during meal breaks" and "she admitted to having spent more than half of her time in court playing the game." And she didn't think it was a problem, saying "yes, it helps me keep my mind busy paying more attention. 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," per the Associated Press. 

With the jury's attention clearly compromised, the judge decided to declare a mistrial. According to the Morning Herald, the trial, to that point, "cost more than AU$1 million, including counsels' fees, staff wages, and court running costs for 60 days of hearings." 

But the jurors weren't punished. There was no law that prohibited jurors in the jurisdiction from playing Sudoku or otherwise not paying attention -- the jurors simply got sent home. Per the AP, the defendants were retried, but the end result of their case is difficult to determine.