William Kennedy Smith is an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 physician

Physician

A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 whose work focuses on landmines

Land mine

A land mine is usually a weight-triggered explosive device which is intended to damage a target—either human or inanimate—by means of a blast and/or fragment impact....

 and the rehabilitation of people disabled by them.
He is a member of the prominent Kennedy political family and is famous for a well-publicized 1991 rape trial in which he was acquitted.
Smith is the second of four children of Stephen Edward Smith

Stephen Edward Smith

Stephen Edward Smith was the husband of Jean Ann Kennedy. He was a financial analyst and political strategist in the 1960 United States Presidential campaign of his brother-in-law, John F. Kennedy.-Biography:...

 and Jean Kennedy Smith

Jean Kennedy Smith

Jean Ann Kennedy Smith is an American diplomat and a former United States Ambassador to Ireland. She is the eighth of nine children born to Joseph Patrick Kennedy, Sr. and Rose Elizabeth Fitzgerald and is their last surviving child. She is the sister of the 35th U.S. President, John F. Kennedy,...

. His mother is the daughter of Joseph P. Kennedy, Sr.

Joseph P. Kennedy, Sr.

Joseph Patrick "Joe" Kennedy, Sr. was a prominent American businessman, investor, and government official....

 and Rose Fitzgerald Kennedy

Rose Fitzgerald Kennedy

Rose Elizabeth Kennedy was the wife of Joseph P. Kennedy, Sr. and the mother of nine children, among them United States President John F. Kennedy, United States Senator Robert F...

. He is the nephew of President John F. Kennedy

John F. Kennedy

John Fitzgerald "Jack" Kennedy , often referred to by his initials JFK, was the 35th President of the United States, serving from 1961 until his assassination in 1963....

 and Senators Robert F. Kennedy

Robert F. Kennedy

Robert Francis "Bobby" Kennedy , also referred to by his initials RFK, was an American politician, a Democratic senator from New York, and a noted civil rights activist. An icon of modern American liberalism and member of the Kennedy family, he was a younger brother of President John F...

 and Ted Kennedy

Ted Kennedy

Edward Moore "Ted" Kennedy was a United States Senator from Massachusetts and a member of the Democratic Party. Serving almost 47 years, he was the second most senior member of the Senate when he died and is the fourth-longest-serving senator in United States history...

.