Using Charts, Diagrams, and Maps in the Courtoom

Using Charts, Diagrams, Graphs, & Maps in the Courtroom

California Objections - Buy NowExcerpted from California Objections: Civil and Criminal

By Judge Gregory H. Ward (Ret.)

Lawyers commonly use charts, diagrams, sketches, graphs, and maps to explain, simplify, or supplement oral testimony at trial. For example, a surveyor may use a map to demonstrate where boundaries begin and end as an aid to expert testimony. A layperson may use or draw a map to describe where an incident occurred. A physician might use a diagram or model to explain medical testimony.

When you ask a witness to step to a map or diagram to show the jury how an event occurred, you signal the jury that these details are important.  The demonstration breaks the monotony of the witness’s testimony and allows the witness to repeat essential evidence in a way jurors can visualize.  Later the map or diagram is an effective aid in closing argument to remind the jury of the testimony.

Tips For Creating and Using Charts, Diagrams, etc.

A diagram or map should be in a form that can be used by the jury and the court of appeal. Do not use a blackboard or whiteboard unless you are prepared to make a copy for the record. When the witness refers to a diagram, make sure the record is clear as to where the witness is pointing, or ask the witness to use a marker to identify specific locations.

Do not put too much information on a single exhibit or chart. If you want to use a diagram later in argument or have the jury consider it during deliberations, do not allow it to be so excessively marked that no one can understand the points to which the witnesses were referring and conflicts in testimony are emphasized. If a chart or visual aid contains too much material, it will confuse the jury and they will ignore it.

Use different colored pens for witnesses or separate clear plastic overlays for each witness.

Label each piece of demonstrative evidence with a brief description that is not argumentative so the jurors will understand how it relates to your presentation of the case.

How to Lay a Foundation For a Chart, Diagram, etc.

Step-by-step guidelines

•             Show the exhibit to opposing counsel.

•             Mark the chart, diagram, graph or map for identification.

•             Have a witness testify concerning his or her relation to exhibit. For example, is the witness an expert? Was the witness at the scene? Did the witness create the exhibit?

•             Have the witness testify as to his or her familiarity with the subject matter, circumstance, or locale depicted in the exhibit.

•             Have the witness testify that the exhibit is a true and accurate representation of what it purportedly depicts.

•             Ask questions designed to illustrate the witness’ testimony through the use of the exhibit.

•             Offer the exhibit into evidence.

Sample dialogue

Counsel (to court): May this diagram be marked as Plaintiff’s Exhibit 3 for identification? Note: Show the item to opposing counsel before it is marked. If you have not done so, show it to opposing counsel at this time.

Counsel (to witness): Are you familiar with the intersection of 1st and Main?

  1.             Yes.
  2.            How are you familiar with the intersection?
  3.             I have lived two doors down for the last 18 years.
  4.            On June 1, 2013, at 3:30 p.m., did you see an automobile accident at the intersection involving a minivan and a pickup truck?
  5.             Yes.
  6.            Directing your attention to Exhibit 3, is this a true and accurate representation of the intersection of 1st and Main?
  7.             Yes.
  8.            Can you take this green marker and draw on Exhibit 3 the approximate locations of the two vehicles immediately after the collision?
  9.             Yes. [Witness marks diagram]
  10.            Please mark the plaintiff’s minivan with the letter “P” and the defendant’s pickup truck with the letter “D.”
  11.             [Marks diagram]

Counsel (to court): Plaintiff offers Exhibit 3 for identification into evidence.

Opposing Counsel: Objection, the diagram is misleading because it is not drawn to scale.

Counsel: Your Honor, it is not important that the map be drawn to scale. I’m only offering it to show the relative positions of the two vehicles immediately after the accident.

Court: Objection overruled.

Objecting to Charts, Diagrams, etc.

The court has broad discretion to admit demonstrative evidence to illustrate a witness’ testimony. People v. Mills (2010) 48 Cal. 4th 158, 207, 106 Cal. Rptr. 3d 153. Courts rarely exclude these items, unless (1) they are not relevant, (2) their foundation is inadequate, or (3) they do not accurately represent or depict the matter at issue. Published charts and maps prepared by persons disinterested in the proceedings may be used to prove facts of general notoriety and interest and are not subject to a hearsay objection. Evid. Code §1341.

Sample objection language

Objection, Your Honor. The [chart] [diagram] [graph] [map] is improper because [it lacks foundation] [is irrelevant] [is unduly prejudicial/misleading and should be excluded under Evidence Code §352].

Tactics for Making The Objection

•             Request a hearing outside the presence of the jury if you believe the information in the exhibit conflicts with the evidence in the case or is unduly prejudicial or misleading.

•            If the exhibit was prepared before trial and contains subjective information that is in dispute in the trial, argue that the exhibit is not supported by the evidence, and in asking the witness to confirm the information in the exhibit counsel is leading the witness.

•             Once a witness has marked on the exhibit, object to its use with subsequent witnesses on the ground that they will be unduly influenced by the prior markings. Point out to the court the potential for conflict among the witnesses and the importance of having independent testimony on the precise locations of various items or persons at the scene.

•             Request that the exhibit remain marked for identification only rather than be admitted into evidence. Argue that the exhibit is cumulative of the witness’ testimony and its admission will unduly emphasize this testimony.

Tactics For Responding to The Objection

•             Specify the evidence that supports the information in the exhibit and make an offer of proof of anticipated testimony that shows the relevance of demonstrative evidence and its usefulness to explain testimony.

•             If the exhibit is only substantially accurate, explain why complete accuracy is unnecessary. Point out that opposing counsel will cross-examine the witness and the jury may consider any inaccuracies in determining the weight to be given to the evidence. Offer to stipulate that the exhibit is not to scale or is otherwise inaccurate in insignificant particulars.

•             If the witness was involved in preparing the exhibit prior to trial, inform the court of this fact and explain that your interest was in expediting the testimony of the witness.

•             Argue that the exhibit is as much a part of the witness’ testimony as the words spoken in court and that the exhibit should be admitted into evidence for consideration by the jury during its deliberations.

•            When the exhibit was used by both sides during the trial, argue that as a ground for its admission. People v. Sassounian (1986) 182 Cal. App. 3d 361, 400-401, 226 Cal. Rptr. 880 (map sketched by witness after conversation with defendant was properly admitted when counsel extensively cross-examined the witness concerning it).

California Cases

Exhibits marked up by witnesses. Witnesses may mark a map or diagram to note physical facts observed by them and in its discretion, the court may admit the marked diagram into evidence. Balasco v. Chick (1948) 84 Cal. App. 2d 802, 808-809, 192 P. 2d 76. A single diagram may be used with multiple witnesses and the court may permit the use of an exhibit previously marked by a witness to examine subsequent witnesses. Although the marks made by one witness could have an influential and suggestive effect on later witnesses, the court may consider the practicalities of the situation in exercising its discretion. People v. Ketchel (1963) 59 Cal. 2d 503, 527-528, 30 Cal. Rptr. 538.

Artistic renderings. Artistic renderings based on interviews with the witnesses may be used to illustrate the witnesses’ testimony if it is shown that the drawings accurately depicted the scenes observed by the witnesses in relevant respects. People v. Thomas (2012) 53 Cal. 4th 771, 805, 137 Cal. Rptr. 3d 533.

Computer animations. Computer animation is comparable to classic forms of demonstrative evidence, such as charts or diagrams. People v. Hood (1997) 53 Cal. App. 4th 965, 969, 62 Cal. Rptr. 2d 137. When used to illustrate expert testimony, computer animation is admissible if it accurately reflects the expert’s opinion. People v. Duenas (2012) 55 Cal. 4th 1, 21, 144 Cal. Rptr. 3d 820.

Charts. Charts are useful to categorize evidence and show the relationship of numerous events or the movement of funds or property. Just as a blackboard may be used to illustrate testimony, prepared charts may be used in the examination of witnesses. People v. Cossey (1950) 97 Cal. App. 2d 101, 112, 217 P. 2d 133 (charts summarizing the transactions contained in the ten counts of the indictment properly used to cross-examine the defendant).

Court did not err in prohibiting an expert’s use of a chart comparing DSM-IV’s symptoms of “major depression” with corresponding criteria for “gang member depression,” a condition recognized by the witness. The witness was permitted to testify as to the information contained on the chart, and the chart misleadingly suggested that there was a scientific basis for the witness’ criteria. People v. Castaneda (2011) 51 Cal. 4th 1292, 1340, 127 Cal. Rptr. 3d 200.

About the Author

Gregory H. Ward is a trial lawyer in private practice in Silicon Valley, and is Of Counsel to McManis Faulkner. From 1990 to 2010, Judge Ward served as a Judge of the Santa Clara County Superior Court. As a judge, he presided over more than one thousand jury and non-jury trials in civil, criminal, juvenile delinquency, juvenile dependency, family, and probate cases.

Prior to his appointment to the Superior Court, Judge Ward was in private practice in Palo Alto, California, where he specialized in business litigation. He also served as Attorney-in-Charge of the San Jose Branch Office of the U.S. Attorney’s Office for the Northern District of California and was a trial attorney for the United States Department of Justice, Organized Crime & Racketeering Section, in Washington, D.C., Chicago and San Juan, Puerto Rico.

He is the author of the legal blog “Developments in California Trial Practice,” where he reports on recent appellate cases and legislation affecting trial practice. Keep up-to-date at

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