Yes they can. They usually don't because the defendant can "plead the 5th". Pleading the 5th refers to the 5th amendment of the constitution which states: "No person...shall be compelled in any criminal case to be a witness against himself". In other words, the defendant does not have to answer any questions.
The prosecutor would rather keep the defendant off the witness stand because the defendant's lawyer can then ask the defendant questions to try to prove his/her innocence. Basically, it often helps the defendant to be a witness in his/her own trial.
The prosecutor would rather keep the defendant off the witness stand because the defendant's lawyer can then ask the defendant questions to try to prove his/her innocence. Basically, it often helps the defendant to be a witness in his/her own trial.