THE POLYGRAPH EXAMINATION ROOM at Royston Police headquarters was conveniently fitted with a one-way mirror. In a small room behind this mirror stood Inspector Matthew Walker and his friend Thomas P. Stanwick, who was taking a break from his freelance editing to observe a slice of a criminal investigation. “You may have seen something in the paper of the Bulgarian Diamond Mining Company securities scam,” said Walker. “Over half a million ‘invested’ dollars were stolen. Of course, there was no such company.”

“And these four were involved?” asked Stanwick, peering through the glass into the polygraph room.

“That’s right. Louis Lambert, Diane Sorensen, Morty Cameron, and John Thorpe ran the whole operation. One of the men was the salesman, another of the four printed the phony stock certificates, another kept the books, and the fourth acted as the banker, depositing and withdrawing the funds. We’re questioning them now about their roles in the scam.”

As Stanwick and Walker listened, the four suspects were given polygraph examinations. Each made two statements. “1 was the bookkeeper,” declared Lambert. “You know what? Thorpe was the bookkeeper tool” He cackled with laughter. “Lambert was not the banker,” said Cameron. “I printed the certificates.”

“Lambert wasn’t the printer,” Sorensen said. “The salesman was Thorpe.”

“Either Diane or Morty kept the books,” said Thorpe. “Diane doesn’t know a thing about printing.”

It was soon apparent that the four suspects would say no more, so Stanwick, who had be en taking notes, departed. He returned the next day to visit Walker in his office. He found Walker glaring at the report of the polygraph examiner.

“1 can’t believe it!” Walker roared. “The polygraph is acting irregularly again. I’m told that each suspect made one true statement and one false statement, but that we can’t tell which is which I’ve got to persuade the chief to budget a new machine.” Stanwick laughed heartily.

“1 hear that polygraphs are notoriously unreliable,” he said. “If that report is true, though, a little logic can determine which statements were true, which were false, and who played what role in the scam.

“Who did what in the Bulgarian Diamond Mining Company?

Scroll down for the answer.

Mini Mystery Solution:

The Case of the Bulgarian Diamonds

If Thorpe’s first statement (TI) is true, then both of Lambert’s statements (Ll and L2) are false. This contradicts the premise that each made one true and one false statement, so TI is false and T2 is true. Therefore neither Sorenson nor Cameron was the bookkeeper, and Sorensen was not the printer. Since she was not the salesman either (the salesman having been one of the men), she must have been the banker. This means that Tl is true, so T2 is false and Cameron was not the printer. He must therefore be the salesman.

This proves that S2 if false, so SI is true and Lambert was not the printer. Lambert was therefore the bookkeeper, and Thorpe was the printer. 

Stan Smith was the author of three books of Stanwick mini-mysteries that have been published in nine languages and sold over 120,000 copies.

By Stan Smith