“Have you ever watched a log-jam? You may see them in the swirling rivers of the forests high on the flanks of the Kjolen. … A great mass of freshly cut logs shoots down the river. At broken water one strikes a snag. The mass struggles but cannot go on. It halts, it churns, it crashes. And soon there is a mountain of logs, crushing each other, building with magical rapidity a broken rampart of wood.
“Then the lumberman seeks to discover the log which is causing the jam—the log which is stemming the wooden tide—in a word, the key-log. Aha! he has found it! A tug, a twist, a pull—it snaps out, upends, darts away. And as if Merlin’s wand had waved above the spot, the wall of wood collapses and makes a mad rush down the river. …
“The investigation of a complex crime, my young friends, is much like a log-jam at times. Our logs—our clews—are racing toward a solution. Suddenly—a jam. To our bewilderment the stubborn clews keep tangling, piling up.
“Then the lumberjacking sleuth finds the key-log and, lo! The recalcitrant clews tumble down, range themselves in swiftly moving rows, open and intelligible, and make for the distant saw-mill—the solution.”
—from an address to the recruits of the Stockholm Police Academy on November 2, 1920, by the Swedish criminologist. …
DR. GUSTAF GOETEBORG