Generally speaking, when we seek to introduce real or original evidence in trial we need to authenticate this evince before it will be accepted into evidence by our trial judge. This requires you, as counsel, to demonstrate an “identification of physical evidence”. This identification process involves having the witness identify the evidence as the original evidence and then describing to the court how the witness is sure that the proposed evidence before them today is the same evidence as the witness originally observed. Commonly, when you have real evidence such as this it will have some type of unique characteristic which makes it readily identifiable. If this is the case you can complete your foundation by having the witness testify that she previously saw this same evidence and observed such unique characteristics of the evidence and she currently sees the same identifying characteristics on that real evidence today in court.
There will be times of course when your proposed item of real evidence does not have a unique characteristic which was observed at the time of the incident and can be recalled by the memory of the same witness today in trial. In these circumstances we can prove identity of the object by demonstrating a chain of custody for the given evidence. In these cases you need to call one or more witnesses who can testify to this chain of custody. These witnesses will testify when and where they possessed the object of evidence and how they kept the evidence safe and secure while in their possession. You will need this testimony for each person who physically handled the evidence. You essentially need to show that there were no gaps in the chain of custody where the evidence could have been tampered with or altered. Have each of these chain of custody witnesses testify as to where and when they initially took hold of the object, how they safeguarded the object and how they ultimately passed on the evidence within the chain. This witness should testify that when he or she received the proposed evidence it was in substantially the same condition as it is today in court.
Whenever possible in trial it is good idea practice to use demonstratives to aid the finder of fact. This is particularly true in jury trials where the jurors do not have a general understanding of the topic you are attempting to teach them about. For instance, if you are trying to explain the way in which spinal damage causes nerve damage you will teach your jurors much more effectively with the use of a model to aid the listeners who can see the model while you explain it to them. With the use of a demonstrative model you can make your witness’s testimony much clearer. The model can be held by the trial lawyer as the witness discusses it or alternatively it can be turned over to the jurors so that the jurors can pass the model around amongst themselves and inspect it. The model brings the witness’s testimony to life and provides the jurors with a much more thorough understanding of your subject material.
The question then becomes how do you introduce these demonstratives in trial? The good thing is you don’t have to demonstrate that the item of evidence is what you say it is as you would with an item of real evidence which is a product of the facts of the case. With demonstratives, the trial judge uses his or her best discretion in determining what you can or cannot introduce to the jurors. If your goal is to introduce a model you need to have your witness testify to a couple things for purposes of establishing the necessary foundation. First of all, have your witness testify that she needs to have use of the visual aid in order to effectively present her testimony to the jurors. Then have the witness testify that the model depicts a certain subject matter, the human spinal column for instance. Then have the witness testify how she is familiar with this model and the basis her familiarity with what this model depicts. Then finally, as always, have your witness testify that the model is an accurate depiction of the actual object at issue, the plaintiff’s spinal column for instance. Once your model is admitted into evidence you can request permission to turn it over to the jurors for their inspection.
For certain concepts, you may find it useful to introduce a diagram which depicts a certain setting or subject. For instance, you could have a diagram of the scene of an accident which you could use to help the jurors visualize the testimony of your pedestrian witness. If you want to introduce a diagram to the jurors you simply need to have your witness testify that the diagram depicts a certain setting or subject matter. Have your witness testify that he or she is familiar with the setting or subject matter depicted in the diagram and then have your witness further explain how he or she is familiar with this setting or subject matter. Finally, have your witness testify as to whether in his or her opinion the diagram accurately depicts the setting it is intended to depict. After completing this foundational dance request that your proposed exhibit be admitted into evidence as you ordinarily would. After the judge allows your exhibit into evidence request permission to show or hand the diagram to the jurors for their viewing pleasure.
Whenever you are using a chart in trial consider whether it makes sense to have your witness mark the chart as you are conducting your examination. If the witness says he was driving in a certain car, as portrayed on the diagram for instance, then have the witness mark the location of his car on the diagram. This marking of the diagram helps the jurors visualize and understand the diagram. Moreover, if you are dealing with a long trial you want your jurors to remember how the diagram should be understood as they look at the diagram days or weeks later in deliberations. If your exhibit is clearly marked at that time then there is less chance of it being misunderstood by your jurors later in deliberations. Lastly, by marking your exhibit you help any potential appellate court understand the record as created in trial. If the appellate court is simply reading a record where witness says that “the car was here” as he points to a location on the diagram, well then the appellate court has no idea what he was pointing at as they will not be able to determine where “here” is. On the other hand, if the witness marks the diagram at that location of “here” the appellate court can later look at the exhibit and determine where the “here” on the diagram is.
Photographs are another alternative which can really make testimony come to life. If you have an opportunity to supplement oral testimony with photographs you should do so to aid the jury. The jury will thank you for making the testimony more real and stimulating. If you do wish to introduce a photograph you need to have a witness testify that he or she is familiar with the scene as indicated in the photo. Then have your witness explain his or her basis for that familiarity. Then show the photo to the witness and have the witness tell the jurors that he or she recognizes the same scene as depicted by the photograph and that this photograph is a true or accurate depiction of the scene as it existed at the relevant time. Remember, that you don’t have to use the witness who actually took the photograph. Typically you can use a witness who is simply familiar with that scene as depicted in the photo and they can then verify the photo based on their familiarity with that scene.
The above article reflects some evidentiary rules as promulgated by the Federal Rules of Evidence. Remember that states have their own rules of evidence which may or may not reflect the Federal Rules of Evidence. For more information on this topic I refer you to Edward Imwinkelried, (2012) Evidentiary Foundations which is an excellent book on this subject matter and the source of the majority of my own information, as outlined above, on this topic.