Established Fields of Expert Evidence

This page was last substantively updated or reviewed August 2021. (Rev. # 95446)

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• < Opinion Evidence

General Principles

All fields of forensics is about making associations with available information. These associations can be used by the trier-of-fact to make inferences.

General Medical Practitioner

• an "expert witness in family medicine permitted to give opinion evidence on the diagnosis, prognosis and treatment of injury of all parts of the body, including neck, back and shoulder"
• "qualified as a duly qualified general medical practitioner, licensed to practice medicine in Nova Scotia, and qualified to give opinion evidence on the diagnosis, prognosis and treatment of human beings"
• "emergency medicine diagnosis and treatment"

Medical Specialists

• "orthopaedic surgeon qualified as an expert to give opinion evidence in the diagnosis, prognosis and treatment of knee injuries"

Drug Trafficking

• Expert Evidence in Drug Trafficking

Gangs

Experts have been qualified in several issues related to gangs:

• workings of a motorcycle gangs
• meaning of tear-drop tattoo in street gang
• nature and characteristics of the Hells Angels organization; the main purposes and activities of the Hells Angels organization and whether they constitute the facilitation or commission of serious criminal offences that afford a material benefit to its members.

Firearm Forensics

• "evidence on the subject of the forensic analysis of firearms and ammunitions, including firearm identification, the identification of fired ammunition components as well as ballistics and toolmark identification"
• toolmark and firearms identification
• "give expert opinion evidence on the subject of the forensic analysis of firearms and ammunitions, including firearm identification, the identification of fired ammunition components as well as ballistics and toolmark identification"
• expert in "the theory, operation and identification of firearms", "the examination and identification of fired and unfired ammunition components", "the examination and identification of toolmarks", "the theory and operation of the comparison microscope", "the theory and practice of ballistic assessment."

Injuries

• "qualified as a duly qualified general medical practitioner, licensed to practice medicine in [the province], and qualified to give opinion evidence on the diagnosis, prognosis and treatment of human beings"

DNA Analysis

Described areas of opinion evidence has included:

• "identification of bodily fluids and the forensic aspects of DNA typing."
• DNA experts will not be able to testify as to the likelihood of accidental transfer of DNA.

Problems in DNA evidence can include the possibility of DNA transfer between people as well as confirmation bias where the testers know the identity of the suspect.

There are several types of DNA sample analysis:

• autosomal DNA analysis (atDNA)
• mitochondrial DNA analysis (mtDNA); and
• y-Chromosome DNA analysis (y-DNA)

There are generally two methods of DNA sampling:

• Short Tandem Repeats (STR) [2]
• single-nucleotide polymorphism (SNP) [3]

Y-STR DNA

Y-STR profile is a patrilineal-inherited profile that is only found on male DNA. It will show the odds that a randomly selected male individual unrelated to the targeted person (usually the accused) would match the sample DNA.

Police in Ontario have been using it as early as 2005.

Psychology and Psychiatry

• Expert Evidence in Psychology and Psychiatry

Dog Tracking

Before a judge should consider expert evidence of a specific tracking by a particular dog, the court there must be enough evidence establishing:

• the reliability of the dog breed; and
• the reliability of the specific dog.

The court should be satisfied with the evidence of the following regarding the dog:

• dog's training
• success rates
• susceptibility to distractions, such as irrelevant scents, cats or other dogs.

The handler is expected to give sufficient detail on "the process, sequence and outcome of the tracking, preferably supported by contemporaneously or near contemporaneously compiled notes."

The trial judge should always give a warning to a jury that "such evidence should be evaluated in terms of the facts of the particular case, and that it falls into the category of evidence in respect of which special care needs to be exercised because the source of the evidence, the dog, is not able to be made subject to the usual check and balance of the court system - cross-examination."

Cases where dogs have been qualified:

• R v Sherman, [1997] BCJ No 2472(*no CanLII links)

R v Rackley, 1996 CanLII 8296 (ON SC), 1 CR (5th) 395, per McKinnon J
R v Klymchuk, 2001 CanLII 28406 (ON SC), 155 CCC (3d) 423, per Wein J
R v Nguyen, 1999 BCCA 98 (CanLII), 119 BCAC 62, per Newbury JA

Wording

• qualified as an expert "dogmaster dealing with the use of dogs in criminal investigations, tracking, and for identifying the location of human scent"

Computer-related Forensics

Defined area of qualification:

• area of computer forensics involving the identification, extraction, preservation, and interpretation of storage and recovery of data from electronic media
• child exploitation investigations in relation to peer to peer file sharing networks
• peer to peer file sharing programs including GigaTribe, Limewire, Shareaza, etc.
• the use of EnCase computer forensic software
• “the operation and function of Facebook as a social media portal, and the interpretation of Facebook account records”
• “online cloud storage and internet investigations”

Computer activity logs include:

• System Resource Usage Monitor (SRUM) - used to determine whether activity is software vs user based in userid indicators [4]
• Browsing history

When Qualification is Not Needed

Using Techonology From User's Perspective

It should not be necessary to have the expert testify as to the "basic functions" of computer storage devices. The suggestion seems to be that basic functionality of any appliance is not in need of proof. Similarly, it should not be necessary to qualify an expert to speak to the use of electronic devices, social media website, and other internet applications.

This has been extended to allow that the operation of "everyday technologies" such as social media is not something that an expert needs to explain.

Contents of Devices

When any machine operates in a "predictable, reliable, and notoriously well-known manner", it is not necessary that an expert explain "how the machine or device accomplishes whatever it does." This rule would apply equally for a phone or a GPS device.

Text Messaging

Text messages can be authenticated even if there is no expert evidence or testimony from the sender.

It should not be necessary to have someone testify as to the "sequence and lapsed timing of messages" in a messaging application.

Cell Towers

There may be no need to for expert qualification for the interpretation of cellphone records or description on how cell phones transmit data to towers.

Child Exploitation

It was also found to be valid for a layperson to describe child pornography websites and the search terms and file named associated with them. There is some suggestion that even the workings of file-sharing programs do not require expert qualification.

See also: R v Baxter, 2009 ONCJ 16 (CanLII), per Bovard J

Other Issues

Generally the time and date stamps found recorded on a device or machine is not hearsay as there is no human declarant.

Forensic Pathology

Wording

• "opinion evidence in that field including expressing an opinion as to the causes of the injuries suffered by the deceased and the causes and times of their deaths"
• "opinion evidence with respect to the cause of injuries to the human body and the cause of death."
• "forensic pathology, including the cause and effect of serious injury and sudden death."

Serologist

Wording

• "forensic biologist who was qualified as an expert in relation to the identification of bodily fluids and DNA analysis."

They may need to specify whether the topic of serology concerns the identification of blood, saliva, sweat, semen, or vagina fluids.

Blood Stains

Example Qualified Expert

• "field of forensic bloodstain pattern analysis and to interpret the physical events that give rise to the shape, location, size and distribution of bloodstains" of a "crime scene in order to interpret the physical events that gave rise to its origins."

Introductory Texts

For information explaining the area of expertise see:

• https://www.sciencedirect.com/topics/medicine-and-dentistry/bloodstain-pattern-analysis
• https://www.google.ca/books/edition/Principles_of_Bloodstain_Pattern_Analysi/8_fKBQAAQBAJ
• https://www.google.ca/books/edition/Flight_Characteristics_and_Stain_Pattern/F2hrAAAAMAAJ
• Intro lecture on blood stains (youtube)
• Controlled demonstration videos (youtube)

Forensic Toxicologist

• "opinion evidence in relation to the absorption, distribution and elimination of drugs and alcohol and poisons in the human body, the pharmaceutical and toxicological effects of drugs, alcohol and poison in the human body, and the effects of drugs on the human body with respect to the operation of a motor vehicle"
• "opinion evidence in the absorption, distribution and elimination of alcohol in the human body, in forensic toxicology and the effect of alcohol consumption on the human body."
• "opinion evidence about the absorption, distribution, and elimination of drugs and alcohol in the human body as well as the pharmacological and toxicological effect of alcohol, drugs and poisons on the central nervous system"
• "opinion in the area of forensic toxicology, specifically the ingestion, absorption and elimination of alcohol in the human body, the calculation of blood/alcohol concentrations in the body, the theory and operation of approved instruments and the effects of alcohol upon the human body with respect to the operation of motor vehicles"
• "qualified to give expert evidence with respect to the pharmacological and toxicological effects of drugs, alcohol and poisons on the human body and with respect to the absorption, distribution and elimination of drugs, alcohol and poisons in the human body"
• "the interpretation of toxicological reports and findings"
• "the measurement of alcohols and drugs in bodily fluids and solutions, and the suitability of the samples for analysis"
• "the effect of drugs and alcohol on performance and behaviour, including on the ability of individuals to operate a motor vehicle;
• "the administration and interpretation of drug influence evaluation procedures"

Forensic Aloholic Specialist

• "Forensic Alcohol Specialist and he was qualified as an expert to provide opinion evidence in regards to the absorption, distribution and intake of alcohol in the body"
• "forensic alcohol specialist employed with the RCMP forensic laboratory in Halifax was qualified as an expert in the effects of alcohol on the human body and in absorption and elimination rates of alcohol from the human body"

Footprint Analysis

Footprint analysis has been controversial and not always accepted.

Fingerprints

• "comparison, identification and analysis of fingerprints, which indicates the examination of scenes of crime for latent fingerprints, the use of Automated Fingerprint Identification System (A.F.I.S.) and the search and comparison of fingerprint files in order to establish identity"
• a Forensic Identification Specialist qualified as an "expert in the identification, comparison and individualization of fingerprints."

Arson-related Forensics

• "determination of origin, cause and circumstances of the fire"
• "determining the cause and origin of a ... fire, in understanding burn patterns, the location of the "seat" of a fire, and its movement during the course of a burn"
• "forensic chemistry in the field of accelerant analysis, identification and analysis"

Other Sciences

• "facial mapping"
• "ear print" identification
• Crime scene analysis including staging
• identification based on gait of walk.
• handwriting evidence permitted despite experts inconclusive evidence
• forgery
• Forensic entomology
• “the function, effect, examination, diagnosis and repair of electrical work, problems and hazards” in relation to an Occupational Health and Safety prosecution
• evidence on the "cultural mores within particular communities."

Credibility of Witnesses

A judge should not simply accept an expert's opinion on credibility.

Other Social Science

• the meaning of the "code of silence" and its effect on witness's willingness to tell the truth.
• determining a community standard, typically in reference to an obscenity charge
• interpreting Patois

General expert evidence on false confessions has been excluded as it was not necessary, while opinion specific to the case has been permitted.

Legal Topics

• expert in laws of certain US states on a specific topic

Non-scientific Areas

• "brokering residential mortgages, including NIQ mortgages"
• "translating the content of intercepted calls from the recording to a transcript"

Failed Qualifications

Similar issues have been disqualified:

• A police officer was refused qualification as an expert is risk assessment of an offender in a sentencing hearing.
• profiling of a sexual abuse victim.
• expert on evidence suggesting "staging" of a crime to divert attention
• embedded false subjective memories in children.