Who said "I have studied human nature for sixty years."?

This quote is attributed to Justice Wargrave.

I have studied human nature for sixty years. - Justice Wargrave

"I have studied human nature for sixty years."

Justice Wargrave Knowledge

Character in And Then There Were None

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"Murder is justified when the victim deserves it."

"The guilty cannot hide forever."

"Justice must be served."

"Every man and woman is alone."

"We're not just after treasure. We're preserving history."

"The mind is humanity's greatest tool."

"A tidy room reflects a tidy mind."

"You can learn a lot about a person by how they keep their space."