I am a fictional writer and need info on a poison that can be put in food and is undetectable in autopsy. Symptoms also can't be too messy, no specific time in how long it takes to take effect.
Science and autopsies have reached a point in the modern world where poisons are generally detectable.
The best poisons are ones that break down into elements that occur naturally: succinylcholine(SUX) and potassium chloride. SUX causes asphyxiation and paralysis, however it is a very painful death. Potassium chloride causes severe heart arrhythmias and mimics a heart attack.
These break down to elements natural in the body and would easily be overlooked: succinic acid and choline for SUX, potassium and chloride of course for potassium chloride which is common in heart attack victims due to muscle damage. However both need to be injected and leave an injection site, this may be pesky if your victim does not take any injected medicine or drugs. While these are the least detectable they don't meet the criteria of being ingestable.
Aconite is another great one. It leaves Aconitum alkaloids, but these can only be detected by a gas chromatography/mass spectrometry. Death usually results from paralysis of the respiratory system or cardiac arrest. What is useful about this poison is it can be absorbed through the skin or consumed and only takes 2mg of pure aconite or one gram of the plant to kill. This method is fairly undetectable as long as there is no cause for an in-depth autopsy and it can be ingested.
Depending on your victims history, there are other ways to poison them and make it look accidental, for example if your victim loves blowfish, you could poison them with tetrodotoxin which naturally occurs but is generally removed by a skilled cook in the cooking process.
There is nothing that can kill you directly that an autopsy could not find eventually, your best bet is to use something that is circumstantially deadly but would not look out of place: for instance salamander toxin in a hikers cookware. It just looks like a sad accident.
Swapping prescription medication this works even better if they have risky meds, just switch the contents of the bottles around, lots of people die becasue they do this to themselves.
Deathcap mushrooms mixed into the salad of a home gardener. That one kills a lot of people already. Mostly becasue the symptoms take days to set in, look like the flu at first, and the mushroom looks like the edible ones and tastes quite good.
Lots of people fatally poison themselves all the time just pick an appropriate one.
I'm sure people remember the poisoning of Alexander Litvinenko with a Polonium isotope? Wikipedia says that only a random coincidence allowed the cause of death to be discovered. But from now on I'll bet that in high-profile autopsies, alpha and beta emitters will be tested for as cause of death.
But, I do think the side-effects can be messy...
Victims of oxygen-deficient atmosphere pass out quickly and die. If a victim was to breathe pure nitrogen, say, for a while, he would die. There would be no way to test for nitrogen since it is 70% of the atmosphere and very common in the body. The deceased would have very little oxygen in their blood or tissues, but I imagine this is common to all dead people.
Sorry, I know it's not a food poision, but maybe it will help.
See also the book The Poisioner's Handbook. But, it's mostly about how poisions can be detected.
I can't think of anything specific, but as has been said, poisons are detectable.
This means that you need to hide it. One way to do that, as has been said is to make the poison degrade into another chemical. However, the remains will still be there.
So I recommend hiding in plain sight:
Use a chemical that is needed by the body, but use a double or triple dose. I remember seeing an episode of some detective series, where someone expresses regret for killing someone by giving them an overdose of a certain vitamin. I don't know if that would be possible, and the chemical would still be there, but people probably won't look for clues in the amount of certain necessary vitamins and minerals.
Another thought I just had is Chirality
A lot of organic molecules have two distinct forms which look the same on paper, but one is needed and used by the body, the other is harmful. These are called the "right" and "left-handed" versions. I once read about a medicine (EDIT: the medicine is Thalidomide (thanks @Nikolai)) released in Germany pre-world-war-II, that caused more harm than good, because they used the wrong handed molecule, well actually both, but the wrong molecule caused quite a few stillbirths if I remember correctly (the medicine was given to pregnant women). I think I remember that humans, and all other life on Earth uses left-handed molecules, so if you give someone right-handed carrots or potatoes, then you could poison them quite badly.
Since the two chemicals are almost the same, it would be undetectable.
Detection is easy enough with mass spectrography these days for blood and tissue analysis.
Insulin is always a good one as the victim just slips into a coma and, with enough insulin, it stops the brain from functioning, long enough in that state and someone dies. Of course if someone finds the person it's very easy for a paramedic to find out they are hypoglycemic and all they need to do is give them a sugar-saline drip.
As insulin is common in the body it used to be missed, but all autopsies now look at all chemical levels of the common types found in blood to see if anything was amiss.
If the victim is a hippy and has not had vaccinations then you could use tetanus bacteria and paralyze them.
Another way would be to use bacteria that can cause meningococcal, then somehow administer it into their eyes (thus straight into the brain), hell if the victim uses eyedrops or contact lenses you can get them to administer it themselves.
Drinking concentrated salt solutions was a method of suicide / execution in China. http://www.nepachemistry.com/2010/12/death-by-common-salt-nacl.html
Our bodies are naturally full of salt. After death, fluids continue to equilibrate by mass action, with salt moving off into tissues and water moving in from tissues to hydrate the salt. It would be difficult to establish that salt was the culprit if any time had passed after death.
- Water. Overdose of plain water can kill. It has happened more than once with water drinking contests. https://www.scientificamerican.com/article/strange-but-true-drinking-too-much-water-can-kill/ The water dilutes out needed electrolytes and causes a heart arrhythmia. After death the water and body salt equilibrate and as with the opposite circumstance above, it is tough to prove what happened.
Technically this meets the OP: can be put in food and undetectable at autopsy. Neither water nor salt has a lot of promise for surreptitiously poisoning someone. Although if you encapsulated the salt somehow such that it was not tasted that might do it.
You might notice the sting of the injection. Within seconds you'd realize you're having trouble moving your eyes and fingers, followed by your arms and legs. If you were standing, you'd collapse. In a heap on the floor, you'd realize nearly every muscle in your body was paralyzed. Being fully conscious, your sense of panic would be rising as rapidly as the paralysis was spreading. Swallowing and breathing has become more and more difficult. Slipping into unconsciousness, your last conscious thought may well be "I am going to die."
From Gizmodo: The History of Sux, the World's Most Discreet Murder Weapon
Read the whole article there.
SUX is a posion that would be good for a crime scene. It is detectable, yes, but it's very difficult to detect. Might be an idea
Pretty much anything can be detected if the detective knows what to look for. A killer's best shot is using a poison that is very rarely used and hence would not be looked for. Succinylcholine is a drug pretty hard to trace. It paralyzes the muscles including those that we use to breathe.
Botulism toxin has medical applications and works in such trace amounts (basically shutting nerves down without being used up in the process) that the principal detection method is trying to replicate symptoms in mice. However, this requires either access to the original ingested substance or significant overdosage (so that viable samples may be extracted from the body of the victim). In addition, it requires a solid hunch regarding the cause of death (nominally asphyxiation): you don't test for it without reason.
I consider it likely that medical supplies are tagged with marker substances but it's not all that hard to cultivate on your own.
Use Ricin, or, even better, a similar protein.
Ricin is a toxic protein produced by Ricinus communis. It is toxic if ingested and therefore does not leave any injection mark.
It has the effect of blocking protein synthesis and is therefore toxic to every cell type. Depending on doses it can kill in hours or a few days.
It's historically been used for assassiantion and therefore its synptoms are well known, however:
Synptoms may vary from person to person, also, it is possible that a purer for of the protein may have fewer symptoms
there are no common clinical tests for Ricin poisoning, bu it can be detected in 2 ways, DNA amplification and antibodies essays.
What to do then? Use a different protein. There are many protein similar to Ricin, Abrin for example is lethal at even lower concentration which makes detection harder; even better you can DESIGN a different protein. Use genetic engineering to remove the part of the protein that binds to the antibodies so that it won't be detected with antibodies essays and instead of extracting it from the beans express it in a vector and then purify it(in this way the DNA detection won't find any traces)
As other answers have suggested, poisons that can't be detected are basically a thing of the past in the modern world. Pretty much anything that has ever been identified as a poison can be tested for, and if there is a reason to do so it will be tested for. Your only hope of having the poison undetected, therefore, is giving the investigators a reason to stop looking: a plausible explanation for why the victim died that can be chalked up to accidental circumstances.
I don't know what the circumstances of your plot require, but one possible approach would be rather than have your victim poisoned you could have the perpetrator drug them instead. This is particularly possible without looking like an issue if the victim regularly uses sleeping tablets, or is a recreational depressant user (e.g. opiates like heroine or opioids like codeine). Then, when they're insensible, inject a massive dose of alcohol. A cursory examination will show that they've gone to sleep under the influence of too much drink and drugs that react badly with it, and died of the consequent alcohol poisoning. Verdict: death by misadventure, investigation closed.
As working in cardiology, I see frequent mistaken ODs with high doses of Cardiology drugs Digitalis is frequent. However, Beta Blockers at high doses, Calcium Channel Blockers with Negative Inotropic effects can cause "Heart Block" and thus heart Failure. This Scenario was suggested in the TV series "DEXTER" for his step father, Harry. Many people OD themselves on their prescribed medications by accident verses purposely, but most often EMTs are CALLED to bring them in by a relative or friend? So, the case would need to be done in a more remote area as happens with backpackers or wilderness campers. The issue is what would the victim with a Heart ailment be doing out in a wilderness area and what would the authorities think of the companion survivor. However, it happens with WIFE survivors with their husbands frequently on vacations without suspect? Not always so, the other way around without suspect--ha ha! Try an angry wife villain with good assets but not a large Life Insurance? Rich Husband OK, Rich wife not so good ha,ha! Although Divorce works well for women without physical murder for obtaining assets. Mrs Scarlett did it with Atenolol in the RV??