"Once entered, a guilty plea cannot be withdrawn except by leave of the court, within its sound discretion, and a denial thereof is reversible only if it appears there has been abuse of discretion." State v. Spence, 29 Conn. App. 359, 363, 614 A.2d 864 (1992). Practice Book 39-27 delineates the grounds for allowing a defendant to withdraw his or her guilty plea after it has been accepted by the court. The defendant claims in this case that he was denied effective assistance of counsel in violation of article first, 8, of the Connecticut constitution and, therefore, should have his guilty plea withdrawn pursuant to Practice Book 39-27 (4). To withdraw his guilty plea, the defendant must prove that counsel's assistance was ineffective and that it was this ineffectiveness that rendered the guilty plea involuntary. Myers v. Manson, 192 Conn. 383, 393, 472 A.2d 759 (1984).