I heard Poirot chuckle softly beside me.

"How did you know?" I whispered.

"Listen."

"I should say"--the doctor was continuing--"that I would have
been considerably surprised at any other result."

"Why?"

"Simply because strychnine has an unusually bitter taste. It can
be detected in a solution of 1 in 70,000, and can only be
disguised by some strongly flavoured substance. Coco would be
quite powerless to mask it."

One of the jury wanted to know if the same objection applied to
coffee.

"No. Coffee has a bitter taste of its own which would probably
cover the taste of strychnine."

"Then you consider it more likely that the drug was administered
in the coffee, but that for some unknown reason its action was
delayed."

"Yes, but, the cup being completely smashed, there is no
possibility of analyzing its contents."

This concluded Dr. Bauerstein's evidence. Dr. Wilkins