Sherlock encounters many murders and the most confusing murders are the ones that involve poisons. Here are four of the most deadliest poisons in history and many have been used to commit murders.

1. Ricin

Ricin is a toxic protein, found in caster bean plants. This poison attacks individual cells in your body and inhibits protein creation. The toxic spreads and affects the whole body, one cell at a time.

Symptoms:

dehydration

diarrhea

fever

low blood pressure

The duration of the poison can last from 24-72 hours. The poison will eventually cause organ failure and death.

An interesting case of ricin poisoning was the assassination of Georgi Markov. He was journalist, in Bulgaria, during a communist regime. A man walked by and shot a micro engineered ricin pellet at Markov's calf. The assassination was successful, because of the size of the poison and the murder weapon, was an umbrella.

2. Batrachotoxin

Batrachotoxin is interesting, because most of us have heard of it. It is found on a particular frog, called the golden poison frog, native to western Columbia.

The frog produces this toxin during a fight or flight stage. It will begin to excrete a milky substance, and uses it as a defense mechanism. It is extremely deadly because it blocks all nerve signals, permanently. This stops muscles from contracting, causing heart failure and paralysis. There is no known antidote for the neurotoxin.

3. Insulin

Insulin is designed to lower you blood sugar and maintain optimal levels for overall health. The body naturally produces insulin to control the blood sugar. People that have abnormally high blood sugar levels, take insulin shots to control the balance. High levels of insulin causes hypoglycemia, low blood sugar. The overabundance of insulin causes the blood cells to disperse and lower drastically. Less blood, equals less oxygen to the body and brain. A severe hypoglycemia can cause seizures, unconsciousness , or death.

The earliest recorded insulin murder was in 1957, Elizabeth Barlow. She was overdosed by her husband and almost got away with it. A jury found him guilty, due to new technology that determined the amount of insulin left in her body. There was also two missing insulin bottles that he couldn't account for.

4. Arsenic

Arsenic is one of the oldest poisons, because it was one of the scariest. It is presented in a powder form to its victims and administered in small quantities. This allowed the poison to work effectively, while it remained invisible to the victim.

Symptoms :

blood in urine

stool

vomiting

convulsions

muscle cramping

Sever symptoms:

led to loss of sensations

cancer

liver disease

diabetes

death.