Week 5: Evidence / Expert Testimony

What is evidence in the criminal justice system?

Evidence is any ( relevant) item or information used to make a fact more or less probable, which is gathered through investigation and required to bring charges.

Who determines if evidence is admissible?

The judge.

What are the main types of evidence? [ Truth Proven During Forensic Neuro Documentation ]

Testimony (eyewitness, expert, victim, police)

Photos/videos

DNA

Fingerprints/bitemarks

Neuroscientific evidence

Documents.

What is expert testimony?

A sworn opinion from a specialist to help the court understand complex issues beyond common knowledge.

What happened in R. v. Mohan?

• Mr. Mohan, a pediatrician in Ontario, was charged with four counts of sexual assault involving female patients.

• During a voir dire (pre-trial hearing), a psychiatrist testified that Mohan did not fit the typical profile of someone who would commit such crimes.

• The psychiatrist’s profile-based opinion was ruled inadmissible.

What are the 4 Mohan criteria?

Relevance; Necessity; The absence of exclusionary rule; Properly qualified expert.

What is relevance in Mohan?

the threshold of relevancy must be met in addition to a cost-benefit analysis balancing probative value vs prejudicial effect.

What is necessity in Mohan?

Expert evidence only allowed if judge/jury cannot form conclusions alone.

What is absence of exclusionary rule?

Evidence is admissible unless a rule requires exclusion.

What is a properly qualified expert?

Someone with specialized knowledge from study or experience.

• Note that the criteria is vague about what makes someone qualified.

What is a risk of expert evidence?

Experts may disagree; opinions are subjective, not facts.

What are the 3 types of opinion evidence?

Expert scientific; Expert non-scientific; Lay ( normal ) opinion.

What is expert scientific evidence?

An opinion based on scientific methods, testing, and research, presented by an expert to help the court understand technical issues.

Novel science requiring reliability and stricter scrutiny.

What are the Daubert criteria?

Used by courts to assess whether scientific expert evidence is reliable and admissible. The four factors evaluated include:

Testability; Peer review/publication; Error rate/standards; General acceptance.

What is expert non-scientific evidence ?

An opinion given by an expert based on specialized knowledge, training, or experience — NOT on strict scientific testing.

What is lay opinion evidence?

Non-expert opinions that assist the court (e.g., police observations).

What is neuroscience?

Study of the nervous system and its cognitive/behavioral functions.

What is neuroscientific evidence used for?

Used to argue competency, mental state, brain damage, etc. during capital punishment, violent crimes or sexual assault sentencing.

Why is neuroscience persuasive?

it is seen to provide a window into the cognition and emotions that drive human behavior; therefore, this information may be overly influential with it being a “hard science” making it “more real” .

What are neuro-fallacies?

Oversimplifications or misinterpretations of neuroscience.

• This is because we don not effectively understand the actual value the scans/ findings are providing.

What is neuro-realism?

Belief that brain images show objective reality.

How does neuroscience evidence affect jurors?

FMRI findings Increased guilty verdicts unless jurors are educated, however, there are No significant difference between other types of neurosciences (e.g. images, graphs, or scans).

What is the overall impact of neuroscience evidence shown in mock-juror studies?

Persuasive but not dramatically changing conviction rates.

What are endogenous and exogenous factors in video & visual Evidence?

endogenous: Internal factors like beliefs and attitudes.

exogenous: External factors like video features and context.

These factors can be used to influential towards a jurors perceptions of visual evidence.

Why is video/ visual seen as strong (probative) evidence?

Viewers tend to believe that these images represent the objective reality accurately and truthfully.

Additionally, The characteristics of video evidence make it especially persuasive include:

• More vivid than verbal evidence (picture superiority effect)

• Makes jurors feel like they are witnessing the real event

• Leads jurors to assign it high probative value

What is the limitation of video evidence?

Only shows a thin layer of facts— meaning that it does not show the entirety of situation, rather the figment captured on the visual.

What is naïve realism?

Belief that we see reality objectively.

• This belief can increase over confidence in beliefs and judgements.

Why is video overvalued?

Compared to listening to testimony, attending visual evidence tends to be more entertaining and occupies more cognitive resources associated with thoughts and memories.

What is attentional focus bias? [ endogenous ]

People notice some things and ignore others.

How do prior beliefs affect perception? [ endogenous]

Prior beliefs and attitudes can cause people to interpret the same video or evidence differently. Instead of seeing things objectively, jurors may notice details that fit what they already believe and ignore others

How do motivations affect perception? [ endogenous ]

current motivations can cause jurors to perceive visual evidence in a way that supports their goals, desires, or expectations

What is the Kuleshov effect? [ exogenous ]

People will interpret an person’s identical facial expressions as happy or sad based on the emotional context of the prior scene.

What does semilegible mean? [ exogenous ]

evidence (like video) is partly clear but still unclear or incomplete in important ways, making them ambiguous and open to interpretations.

Illusory Causation [ exogenous ]

When people incorrectly assume that one action caused another, even if the relationship is unclear or coincidental.

What is camera perspective bias? [ exogenous ]

Camera perspective bias is when the angle or viewpoint of the camera influences how viewers assign blame or responsibility.

What is slow-motion bias? [ exogenous ]

Slower video makes actions seem more intentional and less violent.

What is the role of audio in video evidence?

Audio can influence how video is perceived by creating context effects such as:

• phonemic restoration → filling in missing speech sounds

• cross-modal effects → one sense influencing another

It also increases immersion and the feeling of “being there,” which can shape how viewers interpret visual content.

What is surveillance?

Top-down monitoring (e.g., police cameras).

What is sousveillance?

Bottom-up recording by individuals.

What affects surveillance video quality?

Pixel density, storage, lens design.

Why is surveillance video limited?

Often semilegible despite being probative.

What defines sousveillance video?

Who records ( victim)

when recording starts ( starts when individual are able, rather than at the start)

duration ( short video, meant to capture a time of interest)

How can video evidence issues be improved?

• Educating lawyers and judges about how video can be misleading

• Giving clearer instructions to jurors about potential biases

• Using experts to explain and interpret video evidence

• Allowing jurors to review videos carefully during deliberations