Kevin Spacey testifies in his own defense in sex assault trial in London

Kevin Spacey arrives at Southwark Crown Court on June 30, 2023 in London, England. The Oscar-winning U.S. actor is charged with 12 counts of sexually assaulting four men in the UK between 2005 and 2013. (Neil Mockford/Getty Images)

Kevin Spacey testified Thursday in his sexual assault trial, swearing in a clear and loud voice to tell the "full truth and nothing but the truth" in what could be the most consequential speaking part of his life.

Spacey began by discussing how he got involved in the theater, joking that his mother would say he began acting the moment he emerged from the womb.

The testimony provided some light history on his life before delving into the serious matter before the court.

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Four men have accused the two-time Oscar winner of sexually assaulting them between 2001 and 2013, describing disturbing encounters that escalated from unwanted touching to aggressive crotch grabbing.

One man who called Spacey a "vile sexual predator" said he passed out or fell asleep at the actor’s London flat and woke up to find the actor performing oral sex on him.

Spacey has denied the charges and is expected to provide a vigorous defense.

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The 63-year-old American actor was one of the biggest stars of the stage, and silver and small screens, when sexual misconduct accusations brought his career to a halt. If convicted, he could face a prison term that would doom his hopes of a comeback.

Spacey told German magazine Zeit in an article published last month: "There are people right now who are ready to hire me the moment I am cleared of these charges in London."

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Spacey has pleaded not guilty to 12 charges that include sexual and indecent assault counts and one count of causing a person to engage in penetrative sexual activity without consent.

Spacey, who owns homes in London and the U.S., is free on unconditional bail.