Murder by dry ice

John Dickson Carr* (1906-1977) was an old-school mystery novelist who wrote clever whodunnits and was known for his locked room mysteries, wherein an “impossible” crime is presented and then solved.

I recently read Carr’s The Case of the Constant Suicides, published in 1940, which is yet another locked room mystery. It takes place in a castle in Scotland, and stars Carr’s most famous creation, Dr. Fell, as the sleuth who solves the mystery.

Don't get too excited about the cover blurb that says “Doctor Fell lays a Scottish ghost . . .” In this case “lays” does not have its modern meaning.

What looks to be suicide is really not, and Dr. Fell, with clues also given to the reader (Carr was an author who believed in playing fair) comes up with the solution. What interested me was an exchange by Dr. Fell with some of the other characters. I wondered as I read this, could this actually work? Could this method by which the victim died, dry ice returning to its gaseous state in a closed room, actually kill someone outside of a novel?

From the book:

    “Let us begin,” pursued Dr. Fell, “with the fact that Angus’s diary records his activities for the past year, as diaries sometimes do. Well, what in Satan’s name have been Angus’s principal activities for the past year?”
    “Mixing himself up in various wildcat schemes to try to make money.”
    “True. But only one scheme in which Alec Forbes was concerned, I think?”
    “Yes.”
    “Good. What was that scheme?”
    “An idea to manufacture some kind of ice cream with tartan patterns on it. At least, so Colin said.”
    “And in making their ice cream,” said Dr. Fell, “what kind of freezing agent did they employ in large quantities? Colin told us that too.”
    “He said they used artificial ice, which he described as ‘that chemical stuff that is so expen —’”
    Alan paused abruptly.
    Half-forgotten memories flowed back into his mind. With a shock he recalled a laboratory of his school days, and words being spoken from a platform. The faint echo of them came back now.
    “And do you know,” inquired Dr. Fell, “what this artificial ice, or ‘dry’ ice, really is?”
    “It’s whitish stuff to look at; something like real ice, only opaque. It —”
    “To be exact,” said Dr. Fell, “It is nothing more or less than liquefied gas. And do you know the name of the gas which is turned into a solid ‘snow’ block, and can be cut and handled and moved about? What is the name of that gas?”
    “Carbon dioxide,” said Alan.
    Though the spell remained on his wits, it was suddenly as though a blind had flown up with a snap, and he saw.
    “Now suppose,” argued Dr. Fell, “you removed a block of that stuff from its own airtight cylinders. A big block, say one big enough to fit into a large suitcase — or better still, some box with an open end, so that the air can reach it better. What would happen?”
    “It would slowly melt.”
    “And in melting, of course, it would release into the room…what would it release?”
    Alan found himself almost shouting.
    “Carbonic acid gas. One of the deadliest and quickest-acting gases there is.”
    “Suppose you placed your artificial ice, in its container, under the bed in a room where the window is always kept closed at night. What would happen?
    “With your permission, I will now drop the Socratic method and tell you. You have planted one of the surest murder traps ever devised. One of two things will happen. Either the victim, asleep or drowsy, will breathe in that concentrated gas as it is released into the room; and he will die in his bed.
    “Or else the victim will notice the faint, acrid odor as it gets into his lungs. He will not breathe it long, mind you. Once the stuff takes hold, it will make the strongest man totter and fall like a fly.He will want air — air at any cost . . .”

Carbon dioxide creates a condition called hypercapnia. According to Wikipedia:

“Symptoms and signs of early hypercapnia include flushed skin, full pulse, tachypnea, dyspnea, extrasystoles, muscle twitches, hand flaps, reduced neural activity, and possibly a raised blood pressure. According to other sources, symptoms of mild hypercapnia might include headache, confusion and lethargy. Hypercapnia can induce increased cardiac output, an elevation in arterial blood pressure, and a propensity toward arrhythmias.”

In severe hypercapnia (generally PaCO2 greater than 10 kPa or 75 mmHg), symptomatology progresses to disorientation, panic, hyperventilation, convulsions, unconsciousness, and eventually death. ” (Emphasis mine.)

Now, to my readers: do not try this at home. I’m pretty sure you will get caught if you try it. At least, I hope so. I wonder if anyone who read this novel 72 years ago — or at any time since, tried killing someone with dry ice?

Why, the very thought chills me to the bone!

*Dickson also used the pen-name Carter Dickson.