Should I memorize the testimony while defending?
Federal Crime Lawyer
If you take notes to the stand, more than likely those notes are discoverable and you may have to give a copy to the other side. An alternative - say you need another document to refresh your memory to answer their question – while you are on the stand testifying. Best of Luck!
Please know: My observations here are for educational purposes only and I do not practice in this jurisdiction. Always consult with a local attorney that can provide not just insight, but all of the applicable local rules and laws defining your situation.
Criminal Defense Attorney
Typically not until your memory fails regarding the topic upon which you are testifying. Written notes can generally be used to "refresh your recollection or memory." A witness cannot testify from notes unless they have exhausted their memory and are unable to recall the specific information contained in their notes. Yes the notes are discoverable by the prosecutor's office (if its a criminal case).
Lawsuit / Dispute Attorney
When you are cross-examined you may not use notes until you need your "recollection refreshed" (hich is an evidentiary part of the hearsay rule in the law). That technical aspect of the evidence is just one of many you must know before testifying.
Also, it is not advisable to merely say over and over "I do not remember" because a jury sees right through that antic.
You have heard it before, but it is real important. You should hire a lawyer to represent you in this court matter. What appears to be a cost savings scheme now most surely will not be a cost savings to you in the long run once the case goes south.
Also, testifying from a "memorized" script bears poorly on any witness' credibility. There are many examples of this the we learn in law school as trial lawyers.