Who knows about it and what can you tell me, in relation to killing someone? What are the most common mistakes when someone gets caught poisoning someone they know?
This link might help for some general info.
If you're going to kill someone with arsenic, you're probably going to use rat poison or something like that. Common mistakes mistakes would be, there being something that shows you bought it(especially recently), and leaving it around the house after the poisoning for the police to find. I think it's obvious in an autopsy.
I don't know much about poison. I find it very impersonal and thus, a dull method of murder.
By impersonal I mean distant - There's no looking into their eyes as they take their last breath because poison is a slow killer, which could take hours or days to kill it's intended victim.
Here is a link though that may interest you (below). It's not directly related to arsenic poisoning as such, but it is related to murder by poisoning.
The Myth of the Untraceable Poison: http://www.dplylemd.com/Articles/Poisonmyth.html
That autopsy show on HBO had one where they talked about a woman that killed a couple of husbands with arsenic. Her name was Blanche Taylor Moore. She did some stuff to try to throw the cops off.
Cyanide works better. It is such a deadly poison it killed it's discoverer.
The Iceman used it in his killings. He'd put it in their food and he said like ten minutes later they would die or have a heart attack.
Its fairly undetectable.
Ricin has been used in political assassinations to. Such as by putting a pellet of ricin in a hidden hypodermic needle and injecting it into the victim. They make feel a slight pain, and then mysterious get sick and die later on.
Both Cyanide and Ricin are hard to trace unless you are specifically looking for it. If the person already has health issues such as heart problems or is a drug user the deaths will be blamed on other events.
"Should be done as gradually as possible so it appears as though a consumed item was contaminated, and over time they eventually got sick."
This is good for picking someone you know. The best cover is to pick people who have nothing to do with you or your life (random killings), as that'd make it that much harder to link back to you.
"By impersonal I mean distant - There's no looking into their eyes as they take their last breath because poison is a slow killer, which could take hours or days to kill it's intended victim."
Sometimes killing someone's not for pleasure. It's both the tactician's and the coward's preferred method.
Personally, I'd say picking a poison that's likely to be consumed by the subject would be an ideal cover as opposed to picking an obvious poison. Drugs are basically poison, but a common drug user overdosing on it won't surprise anyone for example. Typical poisons are better if there's a way to remove yourself from the suspect equation.