In a special interview Sunday on NBC’s "Dateline," O.J. Simpson prosecutor Marcia Clark looks back on the high-profile case more than 20 years later.

Clark said she felt "horrible" about losing the murder case against Simpson, who was accused of murdering his ex-wife Nicole Brown Simpson and her friend Ron Goldman.

"It was physically painful. You know, that was not justice," said Clark. "And I thought of Ron and Nicole and thought, this is wrong. It’s so wrong."

Clark said she blames herself for losing the case, though told "Dateline" that she felt there was "no way" to convince the jury that Simpson was guilty.

Clark’s interview comes as a former Los Angeles police officer turned in a knife that was allegedly found near Simpson’s house more than a decade ago. Harvard Law Professor Alan Dershowitz said he believes that it adds more intrigue to the case.

The full interview with Marcia Clark airs Sunday on "Dateline" on 7NBC.

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