You should hire a lawyer with whom you can discuss these things. I assume that you are saying that you were entrapped into committing some act (which is why you are talking about coercion & predisposition.) The law of entrapment says that the officer or their actor did something that was so coercive - that essentially made you commit the offense. (For example, told you he had to sell everything he had in his van including this stolen stereo or he wouldn't have $ for a dr to perform heart surgery on his child as necessary in the next two days & the child would die.) It is something that would lead just about anyone to commit an illegal act (in my example, the act of buy known stolen goods - the stereo - to help a friend's child get surgery so s/he would not die.)
However, one cannot be predisposed to commit the act accused which means that say you are the owner of a pawn shop & you have a reputation and have previously been convicted of buy stolen merchandise. It would not matter to you whether the kid was sick or not, if the stereo is a good deal, you are going to buy it. Therefore, even though you were told some big story, it really had no effect on your decision.
As far taking a polygraph - while they are not admissible in court, they can be used by a lawyer to talk to a prosecutor about a dismissal. Moreover, the lawyer can conduct an investigation inquiring into the background and reputation of the officer - get his IAD & personnel files, and talk with lawyer who have had cases with him to see if there are similarities in lies, etc. (In Houston, polygraphs cost between $450 & $600.)
If the prosecutor begins to doubt whether the officer is being honest, he can present the case to a grand jury (which is not normal) and see what the grand jury thinks.
These are just suggestions. Your question sounds as if you have a lawyer giving you advice. If you are not happy with the lawyer, seek the opinion of another lawyer. You may have to pay for the advice but you will be more comfortable with it - it is much better than this venue where there can be no give & take.