8.2: Court Evidence

The California Evidence Code, or Evidence Code, governs the admissibility of evidence in courtroom proceedings. It dictates what evidence can be presented in courtroom proceedings, how that evidence should be presented, and the weight that should be considered for each type of evidence presented. The evidence that is admissible in court is as follows:

• Real evidence: Real, tangible, or physical objects that are present in court to prove a fact (weapons, documents, developed latent prints, etc.) (see also physical evidence)
• Demonstrative evidence: Items that are used to demonstrate or illustrate something related to the case (photographs, diagrams, desktop or CAD models of the crime scene)
• Documentary evidence: Documents that may be presented to prove a fact (reports, contracts, emails, correspondence, checks, etc.)
• Testimonial evidence: Verbal evidence presented by a witness regarding what they experienced, heard, smelled, or saw
• Direct evidence: Evidence that can prove a fact (eyewitness account, video, etc.)
• Circumstantial evidence: Evidence that can propound a fact by inference or suggestion (an eyewitness seeing someone in the area of a crime or fleeing from the scene)
• Hearsay evidence: A statement that is made by a witness who cannot present the same statement in court. This type of evidence is generally inadmissible in courtroom proceedings, but there are 17 hearsay exemptions in the California Evidence Codes
• Expert evidence: Opinion testimony of an expert on a given subject that pertains to the case, as deemed appropriate by the judge
• Digital evidence: Evidence that is stored or captured in electronic form (cellular telephone data, emails, social media, GPS tracking, computer storage devices, etc.)
• Physical evidence: Any relevant object that may prove a fact (DNA, fingerprints, gunshot residue, transfer evidence, etc.)

Other forms of court evidence are admissible evidence, inadmissible evidence, exculpatory evidence, and incriminating evidence. Admissible evidence is that evidence which the judge has deemed appropriate to be presented in court. Inadmissible evidence is that evidence which the judge has deemed inappropriate to present in court. Exculpatory evidence is that evidence that would tend to prove that the defendant did not commit the act for which they are being charged. Incriminating evidence is that evidence used by the prosecution to prove that the defendant is guilty of the act for which they are being charged. Purposely ignoring exculpatory evidence during a criminal investigation, or withholding the information from the court, can result in serious consequences for the detective or investigator.

Comparison Evidence

Of great importance to the courts is comparison evidence. Comparison evidence is that evidence that can be compared by a skilled and qualified analyst to determine if it is of a common origin as another item that has been documented or recovered. There are many applications of comparison analysis including, but not limited to, fingerprint comparison, footwear and tire tread comparison, ballistic and firearm comparison, handwriting comparison, DNA typing, and hair and fiber comparison. The analysis of comparison evidence is essential in forensic science to for a link between the suspect to the crime scene, to confirm the source of materials, and to identify persons associated with the incident. In order to understand comparison evidence, you will first need to understand the difference between class characteristics and individual characteristics.

Class characteristics describe attributes that are common to a group of objects and therefore provide the ability to compare the objects to that group. Consider the tire that you purchase for your car or the work boot you purchased for your foot. As each of these products come down the assembly line, each product will look exactly like the one before and the one after, provided there is not a defect or wear in the manufacturing tooling that occurred between their production. Thus, as in the photograph below, the outsole of this work boot will look exactly like the others making their way merrily down the production line.

Figure \(\PageIndex{1}\): The outsole of a new pair of Bates brand boots (left boot). - Author's collection

The impression left by this boot, if worn for the very first time, would look exactly like a person wearing a boot of the same size that was produced directly after. Although the comparison of this boot impression would be useful to say it is a Bates work boot, men’s size 11, other than that there is nothing to say who wore the boot other than perhaps the size of their foot.

Individual characteristics, on the other hand, are characteristics that are unique to one specific item, resulting either from manufacturing defect, wear, damage, or natural variation, also known as pattern evidence. Although the analyst can no longer say that the item can be compared to the exclusion of all others, they can determine that the item can be consistent with having originated from a common source. Let us look at the outsole of the boot after your author has worn the boot for six months

Figure \(\PageIndex{2}\): The Bates brand boot after six months of wear. - Author's collection

The analyst can see that although the wearer has good foot alignment, the wear is quite unique to the particulars of how the wearer walks, what he has stepped on, and where he has walked. The defects exhibited on the proximal heel and proximal toe were created by stepping on sharp objects. Those defects, as well as the wear pattern, would be transferred to an impression of the boot; thus, allowing that boot to be uniquely compared to the impression. A forensic podiatrist can also compare the wear patterns of the boot with the characteristics of the wearer’s foot. Although the analyst cannot say that it is absolutely impossible for someone wearing a boot of the exact same brand and size to step on the exact same sharp object in the exact same manner that caused a defect in the exact same place, or stepped on the a pebble with the exact same shape that wedged in the exact same groove at the exact same angle, because somewhere in the world this coincidental occurrence may have transpired. However, the chance that these two people just happened to be in the same place at the same time is extremely remote. The same can be applied to pattern evidence suchStyle as fingerprint comparison.

Biological Evidence

Biological and physiological evidence are evidence that pertain to the human body. Biological evidence is any tissue, organ, fluid or secretion related to the body. This may include blood, semen, saliva, excrement, skin cells, sweat, vaginal secretions, or other fluids or organs associated with the suspect or victim. Physiological evidence is quantitative data related to the internal functions of the human body, which can be used to support or refute a fact in court. This evidence is associated with the functions of the brain, heart, hormonal levels, or any other bodily processes as related to different conditions or stimuli.

Chemical Evidence

Chemical evidence is any evidence that requires chemical analysis to determine identification, origination or composition to link the substance to a crime, crime scene, or event. This evidence includes presumptive and confirmatory testing of narcotics or controlled substances, blood or bodily fluids, minerals, paper composition, tobacco, gases, solvents, explosives or gunpowder, fire debris, and alcohol.

Non-Specific or Miscellaneous Evidence

Non-Specific or miscellaneous evidence is evidence that does not fit into the other categories of evidence and may require the interpretation of an expert to understand. Voice-stress analysis, polygraph, photography, videography, fire origin and spread analysis, entomology, Global Positioning data, computer analysis, or anything else that does not necessarily belong in other categories.

Physical Evidence

As previously mentioned, physical evidence is tangible or physical objects that are used in courtroom proceedings to prove a fact. Consider a handgun found in a vehicle that was chased by the police following an armed robbery at a market. The video acquired from the market shows a person, likely a male, wearing a hooded sweatshirt, grey in color, gloves, and holding a black Glock-type handgun. The video outside of the market shows the robber entering a silver Honda Civic sedan without a front license plate. The sedan has a left front fender that has a dent near the headlight assembly. The video also shows that the suspect is the only occupant in the vehicle. A bulletin is released for the suspect vehicle and an alert highway patrol officer observes a vehicle matching the description enter the highway at a high rate of speed. The patrol officer attempts a traffic stop and the chase is on. After several miles at speed exceeding 100mph, the suspect vehicle runs out of gas and rolls to the shoulder of the highway. The male driver runs from the vehicle, but the officer is able to chase him down and to take him into custody. A second patrol officer arrives on scene to make certain the vehicle is secured, and to her surprise, she finds the vehicle occupied by a patient and cooperative male passenger, who is subsequently detained. The passenger is the same height and weight as the driver. The passenger is identified, and, following a records check that revealed an outstanding felony warrant, detained. The officer asked the passenger how he got into the vehicle, to which he stated that the driver picked him up just before getting onto the highway. On the backseat of the vehicle, the officer observes a grey hooded sweatshirt, a mask, a pair of gloves, and a black semi-automatic handgun that resembles a Glock model 19. During an in-field investigation, the passenger informs the officer that the driver was the person who robbed the market. When asked how he knew the driver had committed the robbery, the passenger stated, “He told me after I got in the car.” Is the case closed? Do you charge the driver for the robbery, write your reports, and process the recovered items and video as evidence? Do you use the statement of the passenger in furtherance as your probable cause to charge the driver for the crime? Or does the evidence, both testimonial and physical, represent merely that which is circumstantial to the driver? What about the addition of the second male in the vehicle? At what point did he enter the vehicle? Certainly, the patrol officer was correct to arrest the driver for recklessly operating a vehicle on a highway while in an attempt to evade and elude the lawful traffic stop, and yes, it would appear that there is sufficient probable cause to charge the driver with the robbery, but it would be prudent to allow the forensic scientist to extract additional information from the physical evidence to identify the real perpetrator of the crime. Video analysis identifies the hooded sweatshirt to be consistent with the item of evidence based on the position of the logo and a stain on the right sleeve. The mask and gloves have class characteristics that are consistent with those in the video. The handgun also has class characteristics that are consistent with those in the video. Fingerprint analysis of the handgun reveals a left thumbprint on the right side of the magazine. The thumbprint comparison reveals that it is consistent with having been contributed by the driver. DNA specimen collected from the interior of the sweatshirt reflects two male profiles consistent with the driver and the passenger as contributors. However, subsequent analysis for DNA specimen from the interior of the mask and gloves produced only one contributor, the passenger. Follow-up inquiry conducted by detectives discovered an additional eyewitness of a hotdog vendor who witnessed the Honda leave the parking lot of the market and stop at an intersection of the road where he observed a male exit the backseat of the vehicle, where he was crouched behind the seat, and exchange positions with the driver. The first driver was observed entering the vehicle by the right front passenger door. During an in-custody interview, the driver admitted that they had hoped the police would not be looking for a car with two occupants if the video indicated only one person committed the crime. The appropriate course of action would be to charge the driver with the forementioned traffic violations, conspiracy to commit robbery, and being an accomplice to the crime. An arrest warrant for the passenger for felony armed robbery should be petitioned from the court. It was the analysis of the physical evidence in the case that not only proved the facts of the crime, but identified the participants and their roles, and aided in a reconstruction of the crime. However, as can be seen in the previous scenario, physical evidence may, without further analysis or investigation, be circumstantial in nature. Take for instance a fingerprint developed on a demand note used in the robbery of a bank. Does the fingerprint, when identified, prove that the person who deposited the latent fingerprint on the note was the person who committed the crime? No, the suspect of the crime might have found the paper, which was previously handled by the person who deposited the fingerprint. The suspect may also have asked the contributor of the fingerprint to hand him a piece of paper, and the contributor provided the paper without knowledge of its eventual use. However, if further investigation indicates the contributor was in fact the suspect, then that fingerprint becomes real evidence during the subsequent trial.

Physical evidence does not always fit strictly into one category but might be a combination of one or more. Thus, physical evidence is divided into three sub-group types:

• Trace or Transfer evidence
• Indented or impression evidence
• Striated evidence

Trace or Transfer Evidence

Transfer evidence is any evidence that is passed from one source to another through some form of contact. This evidence can be small, latent, or microscopic in nature, and can include fingerprints, epithelial cells, bodily fluids, hairs, fibers, glass fragments, paint chips, soil, ashes, and gunshot residue. Trace evidence is any transfer evidence that can be traced to a specific source, such as fingerprints, DNA, bodily fluids, chemicals, hairs, and fibers. Transfer and trace evidence can link a suspect to a victim, a victim to a suspect, or any person to a crime scene.

Impression or Indented Evidence

Impression evidence is physical evidence that is created by the contact of one object into a softer medium or the transfer of a substance from one surface onto another surface, thus leaving a two-dimensional or three-dimensional mirrored impression of the object. Examples of impression evidence are fingerprints, footwear and tire tread impressions, and bite marks. Indented evidence is faint impressions or indentations left from one object onto another by movement or friction. Examples of this would be the indentation of writing from one sheet of paper to a sheet of paper that was underneath. Firing pin marks, firearm extractor and ejector marks are also examples of indented evidence.

Striated Evidence

Striated evidence is scratches, striations, or drag marks, often microscopic, that are created when a hard object that is in motion contacts a softer surface. These markings can be specific to the hard object or tool that caused them and can therefore be linked to one consistent source. Striation evidence is often discovered by firearms examiners who analyze rifling on bullets, firing pin drag markings, or striations that are transferred to soft metal cartridge casings by the breech or chambers of a firearm.

Digital Evidence

In today’s world, even your toaster knows what time you get out of bed, how dark you like your toaster strudel, and your plans for the day. Even in his advanced age, your author has an unhealthy fixation with his cellular telephone. Your vehicle likely knows where you have been during your driving excursions, and how fast you drove to get there. It may even have a video of you behind the wheel. Certainly, your social media activity can be very useful in criminal investigations; as are internet browser, email, and web search history. Digital evidence is data collected from electronic devices that is generally either stored or transmitted by binary code that can either be used to prove or disprove a fact in court. The importance of digital evidence in courtroom proceedings has magnified over the past decade and will likely rival other forms of evidence in the coming decades. It is the responsibility of the trained digital evidence expert to properly collect, preserve, and analyze the data, and to provide expert witness testimony during court proceedings. Digital evidence can be complex, encrypted, perishable, easily altered, and purposely or accidentally destroyed, and therefore it is essential that the evidence is authenticated and deemed reliable by the highest skill and ethical standards of the analyst.

Types of digital evidence are:

• Electronic communications: Social media posts, emails, text messages, etc.
• Website activity: Browsing history, webpage visits, cookies, etc.
• Transaction and Financial Data: On-line purchases, money transfers, banking transactions, etc.
• Metadata: Generally hidden file information that includes creation dates, authors, device information, etc.
• Cloud Storage Data: Files that are stored on internet-based third-party servers
• Internet of Things (IoT) Data: Data from smart phones, wearable technology, home appliances, etc.