In the 1989 Batman movie[1],

the Joker uses a gas that makes the muscles on your face contract into a "smile" to kill people.

My question is simple; is there currently, or is there a way to make, a chemical that can make someone "smile to death". I imagine that such a substance would cause the muscles in ones' face to contract into a "smile", though it really doesn't matter to me how it works, just that it does. Bonus if you can make the chemical airborne so that we can gas those pesky --insert scapegoat ethnicity or cultural minority here-- with maximum efficiency. Because "if you've gotta go, you might as well go with a smile!" ;-)

I am not going to make it a requirement, but I would absolutely love to hear them laugh maniacally too ;-)

No, not laughing gas. Like in the movie. I cannot explain what happened any better than that.

[1] Yes, after you read the entire question (assuming you did) you will likely backtrack and say "Batman isn't hard-science." I know this and you know this. I don't care, I still want any answers to be based in [hard]science. Answers that are not will be downvoted ruthlessly! If "no, this is completely unrealistic" is the answer, that is fine.

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    $\begingroup$ You may want to add the hard science tag if you want hard science answers $\endgroup$ Aug 22, 2016 at 16:15
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    $\begingroup$ @sdrawkcabdear "Science-Based" and "Hard-Science" are basically the same tag, except Hard-Science requires citing peer-reviewed sources, formulas, etc. An answer that reads like a Popular Science article would be a "Science-Based" answer, and not a "Hard-Science" answer, for example. $\endgroup$
    – Ranger
    Aug 22, 2016 at 16:17
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    $\begingroup$ @sdrawkcabdear science-based is enough. hard-science and science-based both demand a foundation in reality. hard-science simply demands you go the extra mile and provide overwhelming evidence in support of your answers. $\endgroup$
    – Jax
    Aug 22, 2016 at 16:29
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    $\begingroup$ @Twelfth Gas cocktail? One gas to elicit one symptom, another gas for another. As long as they don't react with one another something like this could work. $\endgroup$
    – Ranger
    Aug 22, 2016 at 16:53
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    $\begingroup$ @NexTerren - after a chunk or research, I've found there really isn't a gas that can outright cause laughter. Laughing gas is a bit of a misnomer perpetuated by hollywood as is. Tons of methods to die through gasses, but nothing to force laughter. $\endgroup$
    – Twelfth
    Aug 22, 2016 at 21:09

3 Answers 3


My chief reference here is Appendino et al. (2009), though this possibility was first brought to my attention by this National Geographic article.

The Joker's real-world substance of choice? Oenanthe crocata, a type of water dropwort, later infamously dubbed the "sardonic herb". Ancient Sardinians administered it to the elderly as a sort of sedative, shortly before killing them via various unpleasant methods. However, it large enough doses, it can kill the victim, as the neurotoxins contained in oenanthe crocata can be quite potent (see also Schep et al. (2009)).

The major neurotoxin here is oenanthotoxin (not too creatively named). In short, it binds to the receptors in the central nervous system that would otherwise receive gamma-Aminobutyric acid, better known as GABA. GABA is the major inhibitory neurotransmitter in mammals, meaning that it reduces the chance of sending a signal. If the receptors for GABA are blocked, the nervous system cannot function properly, and the person dies.

Now, oenanthotoxin also causes the risus sardonicus, the "sardonic grin" on the corpses of those given enough oenanthotoxin via oenanthe crocata. This arises from contractions of facial muscles due to the blockage of the receptors for the GABA neurotransmitter.

I haven't been able to figure out how oenanthotoxin could be made airborne, but I'll let the Joker know if I see him. I'm aware of gasotransmitters (see also Mustafa et al. (2009)), but I don't believe that oenanthotoxin is a member of that family.

Also, risus sardonicus can also arise early on from tetanus (according to the CDC); however, most patients with tetanus survive, so it would be a very inefficient poison. That said, according to this page, the Joker deliberately infected a child with tetanus, which led to risus sardonicus - so somebody seems to have beaten us there! Still, I prefer oenanthotoxin, because it's much more lethal.

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    $\begingroup$ @DJMethaneMan That's an interesting idea. Hopefully, after release, the aerosol wouldn't disperse too much, but Wikipedia says that oenanthotoxin has an LD$_{50}$ of 0.58 mg/kg, meaning that you don't need a lot to kill a human. Maybe that scheme could work pretty well. And now I'm scared. $\endgroup$
    – HDE 226868
    Aug 22, 2016 at 19:01
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    $\begingroup$ I would have been okay with two separate substances - one for the grin, and one to cause death. But... wow. $\endgroup$ Aug 22, 2016 at 22:42
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    $\begingroup$ Why are we upvoting this? People live in Gotha *ccctt* It's fine. We don't live in Gotham City. He he he. $\endgroup$
    – wizzwizz4
    Aug 23, 2016 at 14:42
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    $\begingroup$ @HDE226868 That is a very high amount for an aerosol to deliver. Just for reference, an inhaler delivers about 0.09 mg. An average man would need 46 mg to have a 50% chance of dying. $\endgroup$
    – Bishop
    Aug 23, 2016 at 14:47
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    $\begingroup$ @Bishop okay, so it's an aerosol firehose $\endgroup$ Aug 23, 2016 at 17:22

To amplify a couple of points in HDE 226868's answer:

  1. Oenanthotoxin and many other toxins that are solid at room temperature can be made airborne by binding them to an aerosol solvent. Tear gas, for example, uses a dichloromethane solvent to disperse what would otherwise be a fine crystalline solid. This even makes a rather dense cloud, like what we see in the movie.
  2. Joker gas could be a combination of different chemicals. He could have combined one toxin that causes risus sardonicus with another that does the actual killing - a nerve gas, maybe.
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    $\begingroup$ And if we want to have the laughing too, introduce a third agent, like laughing gas or some kind of weak asphyxiating agent, to make people gasp while smiling in a sort of grotesque "laugh". $\endgroup$
    – Adam Wykes
    Aug 23, 2016 at 15:17

This is a little more creativity to get the desired effects. Ultimately our joker is using a nerve agent or 'nuerotoxin' of some type. They operate by interfering with the brains ability to communicate with a muscle (can go further here, it's interfering with the sodium component of your muscle, causing it to mass contract). Most common form of death here is actually asphyxia...your diaphragm that controls breathing is ultimately a muscle and not being able to communicate with the muscle that lets you breathe is a quicker death. This is followed shortly by heart failure/arrhythmia (heart also being a muscle).

So getting something that can mess with your muscle control that kills through the same means is actually quite plausible...if you can't control your facial muscles, you're not going to be able to control your diaphragm and death from asphyxia comes shortly after.

Strychnine was the first path I followed...it's known to cause the same effects risus sardonicus has as described by HDE, but this is oral and a pretty high dosage to get these effects. Sarin and cyclosarin (Iraq/Iran during their conflict) is another possible one here, though I doubt the joker would want to watch his victim smile for days on end before perishing. VX is another line of thought here...never really used and far deadlier than Sarin.

As an alternative...Batrachotoxin. This comes from a frog and is used by certain tribes as a blow dart poison. Same effect as above, though this is known to target the heart a bit faster (15-20 mins) and works in tiny (microgram) levels. A little modification, and perhaps the facial controls can go first. There is around 100 variations of these toxins (including tetrodotoxin...that poison blowfish are well known for) and it's feasible that atleast one of these toxins will have a pronounced affect on ones face causing the painful grin.

The majority of these toxins appear to be water born...getting them into an aerosol form seems feasible as well (kinda a misty gas).

This does leave the potential of a twisted smile on their face (caused more by all muscles in their face contracting) while dying, however the maniacally laughing trait is a bit of a miss on this route.

So option 2.
Contrary to popular belief, laughing gas does not make one laugh...a few popular movies and tv shows have tried to show that laughing gas makes on laugh at all costs, but it's not really true. It will make you high enough that more things seem funny, yes...but it's not forced laughter in the degree our joker wants here. The best I can find for inducing laughter is actually Psilocybin, the active ingredient in psychedelic mushrooms. These will cause a person to laugh uncontrollably for no real reason (along with quite a few other affects), however the experience seems subjective and everyone has a different response. Combining this with another toxin that does the actual killing might ****might**** result in seeing someone laugh themselves to death (1 in 1000?), but it's definitely not a guaranteed outcome.

Ya, painfully contorted smile caused by painfully contracting facial muscles seems to be the only route. No laughing yourself to death I guess.


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