He entered an Alford plea, in which a defendant does not admit guilt but admits there is enough evidence for a conviction at trial.

Source: https://www.twincities.com/2023/01/13/after-24-years-in-prison-minnesota-man-freed-when-court-finds-he-was-wrongly-convicted-of-killing-wife/

Under an Alford plea, Phelps does not admit guilt but acknowledges enough evidence exists to convict him.

Source: https://kwos.com/2023/05/one-of-two-suspects-in-grisly-death-of-a-woman-draws-a-life-term/