Wis. Stat. § 904.10
Evidence of a plea of guilty, later withdrawn, or a plea of no contest, or of an offer to the court or prosecuting attorney to plead guilty or no contest to the crime charged or any other crime, or in civil forfeiture actions, is not admissible in any civil or criminal proceeding against the person who made the plea or offer or one liable for the person's conduct. Evidence of statements made in court or to the prosecuting attorney in connection with any of the foregoing pleas or offers is not admissible.
Wis. Stat. § 904.10
When an accused entered into a plea agreement and subsequently testified at the trials of other defendants, and when the accused later withdrew the guilty plea and was tried, prior trial testimony was properly admitted for impeachment purposes. State v. Nash, 123 Wis. 2d 154, 366 N.W.2d 146 (Ct. App. 1985). Statements made during a guilty plea hearing are inadmissible for any purpose, including impeachment, at a subsequent trial. State v. Mason, 132 Wis. 2d 427, 393 N.W.2d 102 (Ct. App. 1986). A defendant's agreement to sign a written confession, after being told by the district attorney that the state would stand silent regarding sentencing if the defendant gave a truthful statement, was not the result of plea negotiations but negotiations for a confession, and therefore was not inadmissible under this section. State v. Nicholson, 187 Wis. 2d 688, 523 N.W.2d 573 (Ct. App. 1994). This section does not apply to offers of compromise made to the police. State v. Pischke, 198 Wis. 2d 257, 542 N.W.2d 202 (Ct. App. 1995), 95-0183. A no contest plea in a criminal case cannot be used collaterally as an admission in future civil litigation. Kustelski v. Taylor, 2003 WI App 194, 266 Wis. 2d 940, 669 N.W.2d 780, 02-2786. Section 908.01(4) (b) deals with admissions by a party as a general rule, but admissions incidental to an offer to plead are a special kind of party admission: they are impossible to segregate from the offer itself because the offer is implicit in the reasons advanced therefor. This section trumps s. 908.01(4) (b) because it excludes only this particular category of party admissions and therefore is more specialized than the latter statute. State v. Norwood, 2005 WI App 218, 287 Wis. 2d 679, 706 N.W.2d 683, 04-1073. This section prohibits the use of incriminating testimony a defendant gave in order to keep the possibility of a plea bargain open. The state's assertion that this section does not apply when, as here, a prosecutor offers to allow the defendant to plead guilty, failed. Not only does this ignore the basic principle that a defendant can plead guilty with or without the prosecutor's consent, but it would require adding the words "to allow" to the statute. State v. Myrick, 2014 WI 55, 354 Wis. 2d 828, 848 N.W.2d 743, 12-2513.