Case Study

Overview — Based on: People v. Valencia, 257 P.3d 1203, 2011 Colo. App. LEXIS 494 (2011).

The trial court convicted the defendant of sexual assault (rape), first-degree assault, burglary, and false imprisonment arising from a course of conduct involving his former girlfriend. The defendant broke into and entered the victim’s home and hid in the clothes closet until she returned. He attacked her and cut her lip, chin, and neck. He dragged her by the hair and placed her in a shower and raped her the next morning when she regained consciousness. The hospital staff took samples as per rape kit protocol and transmitted them to a state laboratory. Blood evidence taken from the defendant’s ear matched the victim, and his DNA from a saliva swab was found to match DNA samples taken from the victim.

During the trial, the prosecution called an expert witness who testified that the blood on the defendant’s ear belonged to the victim and that sperm found in the victim’s vagina matched the defendant’s DNA profile. The expert witness based her testimony on an examination of laboratory items that she had received from an analyst at the state’s bureau of identification. The expert witness did not describe the source of the items themselves, the packaging in which they were contained, or otherwise identify the source of her information. The items that she described were not introduced into evidence. The defendant objected to her testimony because there had been an insufficient foundation for the expert to offer any sort of opinion.

As a general rule, witnesses must have firsthand personal knowledge of facts in order to be permitted to testify concerning those facts. Expert witnesses are not precisely limited to personal knowledge of the facts and may be permitted to rely upon facts presented to them if it is customary and reasonable to do so in the field of their expertise. The general rule is that expert witnesses may give testimony concerning firsthand observation, through facts presented at trial either by means of a hypothetical question or through other evidence received at the hearing, or through facts that are outside of the record, although not personally observed by the expert, if they are of the type recently relied on by experts in the same field. The expert in this case personally received the rape kit evidence and personally performed tests upon a blood sample, a saliva swab, and certain items in the rape kit. She personally perceived the results of those tests, but she did not testify concerning the source or how they were handled, offer them for introduction into evidence, or describe how the items were marked or identified. In addition, there was no proper evidence establishing that the tested items came from either the defendant or victim, save for the expert’s unexplained conclusory statements.