I need paralegal or lawyer assistance

My client was charged with accessory before the fact to murder. The accused principle at the time was not tried yet because he was undergoing mental evaluation to see if he was competent to stand trial. Me an attorney general then went ahead and stipulated that a murder occurred which we did not require the state to prove up to a murder trial. Ultimately my client was found guilty of accessory before the fact to murder even though the principal had not been tried yet. My client was present at pretrial when the stipulation occurred and he never object to the stipulation. Me and my client discussed with a stipulation is but I never detailed to him the fact that by stipulating that a murder occurred (and the principal hadn't even been tried yet) that the state now have legitimate reasons to move forward with the trial. Had I not stipulated that a murder occurred. The state would not be able to move forward with accessory before the fact to murder trial because the principal hadn't been tried yet. Was I ineffective here and my ineffectiveness prejudice my client ? What's the chances of my client now getting relief from the court of appeals ?