Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
plead (v.)
The past tense is pleaded, pled, or plead (this last pronounced PLED), and the past participle, pleaded, pled, or plead (PLED). Pleaded, the regular weak verb form, is more frequent for both parts of speech, and the pled and plead past and past participle forms are labeled Colloquial by some dictionaries, Standard by others.
Plead not guilty and plead guilty are Standard idioms (His lawyer advised him to plead not guilty [guilty]), and the media almost always uses pled to report a defendant’s actions: The defendant pled [not] guilty.
