How to Solve Murdoku

Every Murdoku case can be solved without guessing. That is not a promise about luck; it is a property each case is checked for before it is published: a solver that only ever reasons forward, never trying an arrangement to see whether it collapses, has to get from the first clue to the verdict on its own. The ten patterns below are the moves it makes, written up so you can make them too.

They are ordered roughly the way you meet them. The first four are about the board itself — rows, columns, and the fact that every line holds exactly one person. The next three are about what clues say about people and rooms. The last three are the ones hard cases are built around: the murder rule, shared objects, and counting the whole scene at once.

Each article ends with a worked example taken from the casebook, chosen automatically from a case where that exact deduction is part of the solve, and a list of cases that need it. If a technique is new to you, the quickest way to make it stick is to open one of those cases and find the moment yourself.

The Techniques

The Last Tile — The most basic Murdoku move: one tile left for a suspect means they stood there. How to see it early. (142 of 142 cases)
Only One Fits the Line — Every line holds one person. When only one suspect can still reach a row, that row is theirs. (104 of 142 cases)
Locked Lines — Two suspects, two columns: those columns are theirs alone. The most common hard Murdoku deduction. (91 of 142 cases)
One Free Tile — A row with one open tile left forces someone onto it — and that takes the column too. (34 of 142 cases)
The Cross — A suspect confined to one row and one column blocks the tile where the two lines meet. (30 of 142 cases)
Clues That Tie People Together — North of Dana, one column west of Bella: how clues that link two suspects work in Murdoku. (50 of 142 cases)
Who Else Was in the Room — Alone in the room, a woman in the room: using company clues to rule out whole rooms in Murdoku. (59 of 142 cases)
Alone With the Victim — Exactly one suspect shares the victim’s room. How the murder rule becomes a deduction of its own. (142 of 142 cases)
Beside the Same Object — Two suspects beside one table: how shared-object clues pin two people at once, and their trap. (22 of 142 cases)
Counting the Whole Scene — No room was empty; one person on a puddle. Case-wide counting clues, read from both ends. (42 of 142 cases)

Strategy

How to Start a Hard Case — Hard cases hide the first placement for many steps. A routine for the opening, so you never stare at a blank board.
Murdoku for Sudoku Players — Coming from Sudoku? Which of your techniques work in Murdoku, which do not, and what is new on the board.
Common Mistakes — The misreadings that break most Murdoku solves: north versus directly above, the victim’s row, beside across a wall.

New to the game? Start with the two rules on the how-to-play page — everything here follows from them. How to play Murdoku — the two rules everything rests on