RIAU24.COM  - A plant called Hemlock Water Dropwort that grows wild on the island of Sardinia and is used in ancient Sardinian death rituals has been used since pre-Roman times to ritually kill parents who are a burden on society.

Old people who can no longer support themselves will be drunk and killed with this plant.
zxc1 The

venom of this plant can cause facial muscles to contract, leaving an eerie smile on the corpse's face.

This plant is closely related to parsnips and carrots, the roots have a pleasant taste, but the whole plant is very poisonous. 

Hemlock Water Dropwort is the UK's most poisonous plant and all parts are poisonous, it is reported that death can occur within hours of ingestion. 

zxc2
It is told that a Sardinian shepherd committed suicide by eating drops of hemlock water, leaving a corpse with a glaring grin.

Hemlock Water Dropwort thrives in moist areas including marshes, lakes, or along ditches. It is bright green, hollow, grooved, hairless, shiny, and up to six feet in height. When cut, the stems emit a yellow liquid.

The potent poison present in the Hemlock Water Dropwort is an oenanthotoxin, described as having a terrifying effect upon ingestion. These include excruciating pain, illness, seizures, paralysis, and ultimately, death.