Sources on the death of Claudius

Was Claudius murdered? Barbara Levick (1990) certainly thinks so. For her, the criticial facts are that both Pliny in his Natural History (three times) and Seneca in his play Octavia take it as fact that Claudius was murdered.
By contrast, the Journal of the Royal Society of Medicine (2002) hows that the facts of his death hardly fit poisoning by mushrooms, and is rather consistent with cerebrovascular disease.

This table will help you compare the different accounts of Claudius's 'murder', and see how they differ:

Tacitus	Suetonius	Dio
In the consulate of Marcus Asinius and Manius Acilius	In the consulship of Asinius Marcellus and Acilius Aviola
Fire from heaven played round the standards and tents of the soldiers; a swarm of bees settled on the Capitol hermaphrodites had been born, and a pig with talons. Each of the magistracies found its numbers diminished	A comet; the striking of his father Drusus's tomb by lightning; and the fact that many magistrates of all ranks had died that same year	A comet, a shower of blood, a thunder-bolt fell upon the standards of the Praetorians, the opening of its own accord of the temple of Jupiter Victor, the swarming of bees in the camp, and the fact that one incumbent of each political office died
Claudius when drunk threatened punish his unfaithful wives	Claudius after an adultery trial lamented his destiny to have wives who were all unchaste, but not unpunished	Claudius was angered by Agrippina and would not endure her behaviour
Narcissus openly embraced Britannicus and endorsed his succession	Claudius openly embraced Britannicus, endorsed his succession and made a will	Claudius displayed his affection for Britannicus
Agrippina and Pallas were lovers
Narcissus became ill with worry and went to Sinuessa		Agrippina sent Narcissus to Campania to cure his gout
Agrippina employed an expert poisoner named Locusta		Agrippina sent for a famous poisoner named Lucusta
Halotus administered the poison	Some say Halotus administered the poison, others say Agrippina	Agrippina administered the poison
Sprinkled on an exceptionally fine mushroom	In mushrooms, a dish of which he was extravagantly fond	In one of the mushrooms … she ate of the others, but made her husband eat the largest and finest of them one, which contained the poison
The mushrooms did not work because of a bowel motion, so Xenophon the doctor administered a fast-acting poison on a feather	The mushrooms did not work because he vomited, so he was given a second dose, perhaps in a gruel	He was carried from the banquet apparently drunk, and the poison took effect during the night
Agrippina delayed whilst she waited for favourable stars – prayers were offered, Britannicus shut in his room, and the palace closed	Agrippina delayed whilst she arranged Nero’s succession – vows were offered, and actors called in