Clip | The Nero Files - Did Nero Poison Britannicus for the Throne?

See how modern science may disprove the widely-accepted story of how Nero poisoned his step brother Brittanicus to eliminate a potential adversary.

Secrets of the Dead: The Nero Files premieres Wednesday, February 20 at 10 p.m. on PBS (check local listings).

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In Tacitus''s account, Nero manages to avoid the taster by slyly placing the poison in Britannicus' drink, rather than his food.

Drinks are also sampled by the taster, but Nero is clever: he has a harmless but very hot drink served.

Britannicus is unable to drink it.

Cold, clear water is added to cool the drink.

The water is poisoned and is poured without being sampled by the taster.

According to Tacitus, the poison races through Britannicus' body, making it impossible for him to breathe or speak.

And all three writers agree: He dies almost immediately.

A potential adversary has been removed.

But there are doubts about the poison plot as the writers present it.

In antiquity, the most effective poisons were plant toxins from yew trees, lily of the valley, hemlock and wolf's bane.

Today, scientists in a modern forensic lab are testing whether any of these poisons could have killed Brittanicus in the manner described.

The poison had to have been both colorless and odorless, otherwise it would have been immediately in the water.

And it had to take effect within seconds.

In order to put the poison in the water, the toxin would have had to be extracted from the plant first.

One way to do this was by boiling the plants.

The more the water is reduced during the boil, the more concentrated the poison will be, but the color and aroma also become more intense.

Even when strained to remove impurities, the color remains.

Tacitus writes that the poison is placed in a jug of water that was used to cool Britannicus' hot drink.

If that was the case, the poison had to have been very concentrated in order to remain effective after being watered down twice.

Nor does the timeline as described withstand close scrutiny.

If a plant toxin is ingested orally, then it takes time for the poison to cross from the digestive system into the bloodstream.

Then it must still be transported to the part of the body where it takes effect.

It is therefore fundamentally inconceivable that death could occur within seconds.