Mass. R. Evid. 1120

As amended through October 3, 2024

Section 1120 - Courtroom Demonstrations, Experiments, and Computer Simulations

(a)Courtroom Demonstrations and Demonstrative Exhibits. Demonstrations or demonstrative exhibits, including chalks, may be presented to the jury but are not part of the evidence of the case and do not go to the jury room in the absence of agreement of counsel.

(b)Experiments. A witness may testify about the results of an experiment if the trial judge finds that the experiment is reliable and sufficiently similar to the circumstances of the issue and that the witness is qualified as an expert in the relevant area.

(c)Computer Simulations. A party may present the results of a computer simulation if the trial judge finds that the simulation is based on a reliable methodology and that the underlying data is sufficiently complete and accurate.

Mass. Guid. Evid. 1120

This section is derived from Commonwealth v. McGee, 469 Mass. 1 (2014), and Commonwealth v. Rintala, 488 Mass. 421 (2021).

Subsection (a). Demonstrative evidence is used to illustrate witness testimony or assist in closing argument. It may consist of physical evidence such as a replica or model; a physical demonstration; or charts, chalks, or photographs. Commonwealth v. McGee, 469 Mass. 1, 7, 9-12 (2014) (six-year-old child witness allowed to use a couch to demonstrate how victim was positioned as defendant killed her); Goldstein v. Gontarz, 364 Mass. 800, 814 (1974) (counsel was allowed to use blackboard during closing argument to show estimated total damages). To be admissible, demonstrative evidence must (1) be a fair reflection of the facts or data that the proponent seeks to clarify and (2) create circumstances similar to those described in the witness testimony. Commonwealth v. Makarewicz, 333 Mass. 575, 592 (1956); Commonwealth v. Noxon, 319 Mass. 495, 536-537 (1946). See Commonwealth v. Shiner, 101 Mass. App. Ct. 206, 217-218 (2022) (where Commonwealth sought to communicate to jury how object seen using a night-vision camera might look different from how object would appear to naked eye, concept could be introduced through testimony of lay witness as a demonstration, rather than as an experiment requiring expert testimony). Proposed demonstrations need not exactly replicate the facts in evidence. Ducharme v. Hyundai Motor Am., 45 Mass. App. Ct. 401, 408 (1998). See Commonwealth v. Perryman, 55 Mass. App. Ct. 187, 193-194 (2002) (permissible for jurors to look through telescope that arresting officer used to view drug transaction).

Demonstrative exhibits should not be formally admitted in evidence or sent to the jury room unless the device is merely a summary of already admitted evidence, the parties agree, and the judge allows it. Commonwealth v. Wood, 90 Mass. Appt. Ct. 271, 276-280 (2016); Commonwealth v. Walter, 10 Mass. App. Ct. 255, 263-264 (1980) (judge allowed chalks depicting direct testimony of insurance adjustor to go to jury room). Demonstrations may be disallowed where the risk of prejudice, confusion, or delay substantially outweighs their helpfulness. Commonwealth v. Corliss, 470 Mass. 443, 454-456 (2015).

Subsection (b). Experiments must be admitted through expert testimony and must (1) be relevant and reliable; (2) be sufficiently similar to the circumstances of the evidence; and (3) not confuse the jury, but rather aid them in their analysis. Lally v. Volkswagen Aktiengesellschaft, 45 Mass. App. Ct. 317, 332 (1998). See Griffin v. General Motors Corp., 380 Mass. 362, 365-366 (1980) (use of ammonia instead of gasoline sufficiently similar to admit results of experiment to determine whether fumes could enter passenger compartment); Ducharme v. Hyundai Motor Am., 45 Mass. App. Ct. 401, 407-409 (1998) (results of crash test admissible even though crash test dummy was not placed in exact position as plaintiff injured in crash). The proponent of the experiment must demonstrate its reliability and the fitness of the expert. Commonwealth v. Rintala, 488 Mass. 421, 427 (2021).

Cross Reference: Section 702, Testimony by Expert Witnesses.

Subsection (c). A party offering a computer-generated model or simulation must treat it as a scientific test and show that (1) the computer is functioning properly, (2) the input and underlying equations are sufficiently complete and accurate and have been disclosed to the opposing party, and (3) the program is generally accepted by experts in the respective field. Commercial Union Ins. Co. v. Boston Edison Co., 412 Mass. 545, 549 (1992); Schaeffer v. General Motors Corp., 372 Mass. 171, 177-178 (1977).