“I’ve a good mind to take you at your word, and you’ll have only yourself to thank if it bores you. To begin with, then, there are three basic points on which a prosecutor has to satisfy the judge—or the jury, if it’s a jury case. These are: opportunity, method, and motive. It isn’t absolutely necessary to prove motive; but one does what one can to establish it if possible. A jury might be chary of convicting unless they saw something of the sort.” “You might expand that a bit,” Wendover suggested. “All you’ve given me is three words.” “Take them one by one,” Sir Clinton went on. “First of all, opportunity. The accused man must be somebody who had a real chance of committing the crime—somebody who isn’t excluded by ordinary physical impossibilities. If a body with its throat freshly cut were to fall into this room at the present moment, it would be no use trying to bring a case against the Mikado or the President of the United States. We know that they’re thousands of miles away at this time. It would be physically impossible for them to have done the trick.” “That’s self-evident,” said Wendover. “A murderer’s bound to have been on the spot when he committed his murder.” “Not necessarily,” Sir Clinton contradicted at once. “A poisoner needn’t be near his victim when the victim dies. He might have sent poisoned chocolates by post or something like that. But he must have had the opportunity of committing the crime, whether he was on the spot or not. You couldn’t have accused Robinson Crusoe in a poisoned chocolates case; he was outside the postal radius.” Wendover nodded in agreement. “But in this particular case at the Maze,” he commented, “it’s pretty plain that the murderer was on the spot all right. The person who killed the Shandons was somebody who was in or near the Maze between three and four o’clock this afternoon.” Sir Clinton passed to his second point. “Method is the next thing. It’s an axiom that the more ordinary the method of killing is, the more difficult it is to spot the murderer. Suppose you find a body in a by-street and it turns out that the man has been stabbed to death. What have you to go on? Not much. But if you find somebody poisoned with some fairly out-of-the-way alkaloid, then you limit the number of possible murderers very considerably. You remember the Crippen case. Divergence from the normal is the weakest link in a murderer’s chainmail.” “Well, you ought to be happy in this affair. You’ve got a sufficiently out-of-the-way method.” “That’s so,” Sir Clinton admitted. “But what you gain on the swings you sometimes lose on the roundabouts, you know. The method in this case was one that either a man or a woman could have used. Even a child can pull a trigger. That extends the range a bit.” “But a child would need to have had the chance of getting at the curare.” “And the curare has been lying open to anyone for the last year or two. Don’t forget that.”