Cross examination can be an incredibly powerful tool in trial.  Cross examination allows us use leading questions unlike direct examination.  Cross examination also allows for the examining lawyer to impeach of the witness.  When we impeach a witness we demonstrate that the witness either intentionally lied on the stand or otherwise testified falsely because of memory imperfections.  To demonstrate the lie or faulty memory the cross examiner typically relies on evidence of prior statements made by that same witness.  These prior statements are inconsistent with current statements the witness makes in open court. 

     The law is quite liberal in its restrictions as to who is competent to testify.  The witness need to be able to deliver relevant evidence which that witness has personal knowledge of.  This of course does not apply to expert witness testimony.  To demonstrate that a witness has personal knowledge counsel can simply inquire of that witness as to how that witness has personal knowledge.  The witness can then lay a foundation for his personal knowledge of the subject matter.  A witness who knows of a subject matter because someone else has told him/her about the subject matter does not have personal knowledge of the subject matter. 

     Additionally, there are exclusionary rules which prohibit testimony in certain situations.  Keep in mind that the judge overseeing the case cannot testify as a witness in trial.  Also, sitting jurors cannot testify as witnesses at trial.  Jurors are explicitly precluded from testifying about any statements made in deliberations.   There are however a couple exceptions to this rule.  A juror can testify as to extraneous prejudicial information that was improperly brought to the jury’s attention.  A juror can also testify as to any mistake which was made in entering the verdict on the verdict form. 

     Children are allowed to testify as well, under the federal rules of evidence.  However the court can exclude children from testifying if the court determines that the child is too young to be able to know truth from falsehood.  The trial judge has discretion in this regards.  The trial judge will look to see what the probative value of any such testimony would be before making this determination. 

     Presiding judges have significant latitude in determining the order of presentation of the parties’ cases.  The presiding judge is directed to structure presentation of witnesses and evidence in a way which is effective for determining the truth, avoids waste of time, and protects witnesses from harassment.  Additionally, the trial judge can ask questions of the witness.  However the judge is limited to asking questions which help the court better understand testimony presented.  The trial judge cannot act as an advocate or otherwise question a witness in a way which could be said to support one parties’ case.

     The rules regarding the scope of potential cross examination vary from state to state and from state to federal court.  Some state law allows for what is called the “wide-open” rule.  Under the wide open rule the cross examining lawyer can ask questions on any topic that is relevant to the issue of the trial.  However, under the Federal Rules this “wide-open” rule is not permitted.  Under the Federal rules the cross examiner is limited to inquire in regards to matters touched upon in direct examination as well as questions that go to the witness’s credibility.     

     As mentioned before a lay witness is only allowed to opine on matters in which he or she has personal knowledge of.  This means that the witness is free to testify as to matters personally observed by that witness.  Beyond that the lay witness is generally prohibited from testifying as to his or her opinion.  The trier of fact, jurors, are considered best equipped to reach opinions or conclusions based on facts delivered from the lay witnesses.  However, the court, can allow such lay opinion testimony if it determines that this opinion testimony might help the jurors form a clearer understanding of the witness’s testimony or of facts the witness testified to. 

     Understand that when witnesses are not testifying that they can be, at the request of a party, sequestered or removed from the courtroom.  However a party of the case cannot be sequestered from the court room, nor can an officer or employee of the party who is not a natural person.  Additionally a person whom a party shows necessarily needs to remain in the courtroom in order to sufficiently present evidence.  The chief example of this being the expert witness. 

     A witness’s credibility can be attacked by several different means.  Impeachment by prior inconsistent statement being the chief form of doing so.  This is the process whereby opposing counsels impeaches the witness on the stand by presenting the witness with the witness’s own prior inconsistent statements. 

     There are times when a witness’s credibility can be attacked by presentation of the witness’s criminal history.  The theory behind allowing the presentation of criminal history relies on the premises that those who do not respect our societal rules and laws may also not respect their oath to tell the truth on the witness stand.   The jurors thus can say since this individual lied or was dishonest before that he or she may likely do so again in the future.  This is what we call propensity evidence.  Though there is a general prohibition against propensity evidence the presentation of past criminal history to demonstrate a witness’s propensity is an exception to the general prohibition. 

     Generally speaking the admissibility of this past criminal history is decided at pretrial motion hearings.  Keep in mind that the rule is not carte blanch but rather complicated in determining what is or is not admissible criminal history.  The Federal Rules generally say that for felonies, crimes punishable for more than a year the conviction must be admitted against a witness who is not also the defendant.  That evidence must likewise be admitted in a criminal case in which the witness is a defendant assuming the court determines that any probative value outweighs any prejudicial effect to that defendant.  The requirement that the prior crime must be felonious is irrelevant if the past crime bore on dishonesty or false statement.  Keep in mind that there are further restrictions for admissibility of any prior crime if that crime was adjudicated more than ten years prior. 

     If the prior crime contained an element of proof which required dishonesty then that conviction is generally admissible to impeach any witness, whether or not that witness is the defendant in a criminal trial.  This would include such crimes as fraud, embezzlement, or perjury.  With these types of past crimes there is typically no Rule 403 balancing test wherein the court would balance the probative nature of the impeaching evidence against any prejudicial nature the evidence may carry with it.   

     Know that past bad acts are not treated in the same way as are past criminal convictions.  Though past bad acts are theoretically relevant to credibility just as are past criminal convictions they are nonetheless prohibited for the purpose of attacking credibility.  The rationale for this prohibition is that it would be too time consuming and possibly confusing for isolated incidents of bad conduct to be tried by the jury.  In essence this would require mini trials within the trial itself.  Whereas a conviction does not require the matter to be inquired into as the conviction speaks for itself.  Thus the rationale lies in policy of judicial economy rather than any lack of relevance.  

     There is however an exception to the general prohibition against inquiring into past bad acts that did not lead to conviction.  If the past bad act is one that goes directly to a witness character for truthfulness.  However if counsel choses to inquire as to these past acts related to honesty then counsel is limited to taking the witness ‘s answer as stated.  In other words, the cross examiner is not permitted to impeach the witness with extrinsic evidence.   Essentially all counsel can do is ask the witness a question and have the witness reply, nothing more. 

     Another mechanism for impeaching credibility comes by way of reputation or opinion evidence.  The Federal Rules of Evidence allow a witness’s credibility to be attacked or supported by testimony about a witness’s reputation for having a character for truthfulness or untruthfulness.  Thus an impeaching witness can be put on the stand to testify as to the testifying witness’s reputation for veracity or as to what opinion the impeaching witness has of the testifying witness’s veracity or lack thereof. 

     However, recall that an impeaching witness cannot testify as to specific incidents of conduct by the testifying witness which would demonstrate a lack of veracity.  This type of impeaching testimony is prohibited for policy reasons. 

     Once an impeaching witness has testified as to the testifying witness’s lack of veracity the testifying witness is free to rehabilitate.  This rehabilitation involves using other witness’s to opine on the impeached witness’s truth telling qualities.  Again, the rehabilitating witness is prohibited from testifying as to specific incidents of fact which demonstrate truth telling qualities, rather the rehabilitation witness can testify as to the general reputation of the impeached witness or as to what opinion he or she holds of the impeached witness’s veracity.  Remember that this rehabilitation is not permitted until the witness’s veracity has first been attacked. 

     One of the more common ways of impeaching a witness’s credibility is by way of demonstrating the witness’s bias on cross examination.  This form of impeachment is often done by way of evoking financial gain the witness realizes by way of the party whom he or she testifies on behalf of.  The independent medical examination doctor is a good example here.  The IME doctor being hired by the insurance company to prepare a report and to testify that the plaintiff is exaggerating symptoms.  Cross examination should involve inquiring as to the financial source of income the IME doctor receives from the Defense.  Another common way to demonstrate bias is by showing other ties such as family ties.  These family ties demonstrate bias or motive for the witness to testify in a way which supports their family member’s position. 

     An important note to remember with regard to impeachment is that collateral topics should not be used for impeachment purposes.  In other words, when a cross examiner uses a prior inconsistent statement to impeach the witness’s credibility then that prior statement must be inconsistent with a statement which is relevant to the main issue of the case.  For instance, if the inconsistent statement is one relating to an issue which is not important for the jury in reaching a verdict then it is deemed to be collateral.  If a witness said that the car was blue and then later said the car was red then this evidence is said to be collateral unless the color of the car is of significance to the outcome of the case.  So if the identification of the car was an important piece of evidence then this evidence would not be deemed collateral.  However if the color of the car is of no significance then such evidence is collateral and thus not proper fodder for impeachment. 

     As a final note understand that when counsel uses a prior inconsistent statement, the finder of fact being the judge or jury, are to use this inconsistency as a means for assessing the veracity of the witness.  The prior statement is not supposed to be used as substantive evidence of what really did occur.  However, this in practice is a fallacy.  Jurors are not equipped to compartmentalize information into boxes that solely contain information on veracity and boxes which only contain substantive evidence to be used in reaching a verdict.  Instead, all information is synthesized by the human brain and processed irrespective of what instruction the court may give the jurors as to how information is to be used.