¶33 Wisconsin Stat. § 971.08(1)(b) provides that before a circuit court accepts a defendant’s guilty plea, it must “make such inquiry as satisfies it that the defendant in fact committed the crime charged.” This court has determined that establishing a sufficient factual basis requires a showing that “the conduct which the defendant admits constitutes the offense charged . . . .” White v. State, 85 Wis. 2d 485, 488, 271 N.W.2d 97 (1978) (quoting Ernst v. State, 43 Wis. 2d 661, 674, 170 N.W.2d 713 (1969)); State v. Black, 2001 WI 31, ¶21 n. 8, 242 Wis. 2d 126, 624 N.W.2d 363.
¶34 The duties established in Wis. Stat. § 971.08 are “designed to ensure that a defendant’s plea is knowing, intelligent, and voluntary.” Brown, 293 Wis. 2d 594, ¶23. In our recent decision in State v. Kelty, for example, we allowed that a plea may not be “knowing, intelligent, and voluntary because the plea colloquy was defective in discussing the elements of the crime or the factual basis” for the charges. 2006 WI 101, ¶44, 294 Wis. 2d 62, 716 N.W.2d 886. Thus, establishing a factual basis under § 971.08(1)(b) is necessary for a valid plea. 
¶35 Specifically, the obligation that the circuit court establish a sufficient factual basis helps ensure that the defendant’s plea is knowing and intelligent.  The factual basis requirement “protects a defendant who is in the position of pleading voluntarily with an understanding of the nature of the charge but without realizing that his conduct does not actually fall within the charge.” State v. Thomas, 2000 WI 13, ¶14, 232 Wis. 2d 714, 605 N.W.2d 836. Likewise in Morones v. State, this court noted that “[t]he purpose of the statutory requirement for a court inquiry as to basic facts is to protect the defendant who pleads guilty voluntarily and understanding the charge brought but not realizing that his conduct does not” constitute the charged crime. 61 Wis. 2d 544, 552, 213 N.W.2d 31 (1973); see also Broadie v. State, 68 Wis. 2d 420, 423, 228 N.W.2d 687 (1975). A defendant’s failure to realize that the conduct to which she pleads guilty does not fall within the offense charged is incompatible with that plea being “knowing” and “intelligent.”
¶38 In the present case, the circuit court’s inquiry into the factual basis for the plea (that is, its inquiry into whether Lackershire “in fact committed the crime charged”) was likewise insufficient. After the colloquy there remained a substantial question as to whether the facts that formed the basis of Lackershire’s plea constituted the offense charged. Because of this substantial question, the plea colloquy failed to demonstrate that Lackershire realized that if the underlying conduct was a sexual assault upon her, that conduct could not constitute the offense charged. Like the defendant in White, Lackershire was potentially in the position of pleading guilty without realizing that her conduct did not constitute the offense charged.
¶39 At the plea hearing, the court noted that the criminal complaint and the testimony from the preliminary hearing provided the factual basis for the offense charged. However, neither of these documents unequivocally supports the conclusion that Lackershire admitted to conduct that “constitutes the offense charged.”…
¶41 … Thus, there is a substantial question as to whether these facts, which form the basis of Lackershire’s plea, constitute the offense charged. That substantial question obligated the circuit court to make additional inquiry, pursuant to § 971.08(1)(b), to ensure that Lackershire in fact committed the crime charged.
The court stresses “the unique circumstances of this case,” ¶43, which at least suggests that it will take unusual facts before a faulty factual basis is found. And what are these unique facts? Start with Lackershire’s characteristics, ¶7: “Lackershire is a mentally and physically challenged person. She suffers from learning and cognitive disorders, has a tenth-grade education, and has a history of psychological problems. She is legally blind, and lives on Social Security Disability and Supplemental Security Income payments.” Now, couple her limitations with the idea that the only conduct that she admitted to on this record [sex with a child who raped her] didn’t establish her guilt of a crime, and you get a good idea of why the case is “unique.” The dissent, by turns sarcastic and hyperbolic, is unmoved by either Lackershire’s intellectual deficits or her possible victimization; more to the point: simply fails to meet the majority’s analysis. Instead, the dissent dogmatically asserts: “Lackershire’s admission that she had sexual intercourse (i.e., affirmatively acted or directed action) means that her admitted conduct did not amount to a rape defense,” ¶108. Her admission of sexual intercourse means no such thing, unless it is clear on the record that she, cognitive problems and all, actually knew that she was admitting that she “directed,” or whatever, the sex. Clearly, she had sex; clearly, the other person was underage. And that’s all she admitted, at least on this record. Indeed, the dissent points to no contrary evidence in the record, probably because there is none. But that only goes to show how strong the factual-basis defect must be, and even then it may prevail only by the thinnest of margins.