Have a 1984 conviction that def went to pen on. defendant insists that they are eligible for probation.42.12 Section4e says that they are not eligible. Am I missing something?I also wish I could use the old conviction to impeach the Defendant when he takes the stand. Reversible error?

Obviously, if the defendant fails to file a sworn motion that he has no prior felony conviction, he is ineligible to have a jury consider recommending probation. If he files such a motion which you can prove to be false, then immediately charge aggravated perjury. If the prior conviction was later declared void, then maybe there is a different answer, but that would seem to be the only valid explanation for the defendant's position. See Baker, 520 S.W.2d at 783; Kingsley, 834 S.W.2d at 85.

Use of the conviction under 609 depends on whether the court determines, in the interests of justice, that the probative value substantially outweighs its prejudicial effect, which usually depends on whether there have been any subsequent crimes committed. See Jackson, 50 S.W.3d at 591. The ice is very thin, so extreme caution is necessary.

Thank you for the help and citations. If the jury does not convict I'll have an easy third degree felony.