CSI & Evidence
This core principle states that "every contact leaves a trace."
What is Locard's Exchange Principle?
Forensic document examiners evaluate broad writing characteristics before looking at individual letters; this mechanical trait refers to the measured distance between individual letters and words, which reflects a writer's rhythm
What is Spacing?
If an investigator wants to see if a suspect took a drug today, they test blood or urine. But to see if they were exposed to toxins months ago, toxicologists test this body material instead
What is Hair (or Nails)?
Under the landmark 1993 Daubert standard, this legal figure acts as the active "gatekeeper" who decides whether scientific evidence is valid enough to enter the courtroom.
Who is the Judge?
Before looking for signs of stress or lying, an investigator must spend time establishing this non-threatening baseline control to learn how a subject normally acts.
What is Baseline Behavior?
Video footage of a crime occurring is an example of this major evidence category, which directly proves a fact without requiring any inference.
What is Direct Evidence?
When analyzing physical writing mechanics, examiners look at how hard the author pushed down on the page—a characteristic controlled by muscle memory known as this.
What is Pen Pressure?
In 1836, Scottish chemist James Marsh developed the first reliable chemical test to detect this notorious, odorless poison once nicknamed "inheritance powder."
What is Arsenic?
In a criminal trial, the defendant is presumed innocent, meaning this side carries the burden of proving guilt beyond a reasonable doubt.
Who is The Prosecution (or Government)?
Asking a suspect to describe their alibi backwards from night to morning is an interview technique known as this, designed to test rehearsed scripts.
What is Reverse Recall?
Shoe tread patterns, brand-specific ammunition, and blood types are examples of this type of evidence characteristic, which narrows down evidence to a group rather than a single unique source
What are Class Characteristics?
Forensic document examination focuses on objective physical comparisons rather than attempting to predict a person's this from their writing style.
What is Personality?
This rapidly acting systemic poison halts cellular energy (ATP) production by blocking Cytochrome c Oxidase (Complex IV) in the mitochondria, preventing cells from using oxygen.
What is Cyanide?
Unlike an ordinary eyewitness who can only talk about what they personally saw or heard, this type of witness is allowed to give scientific opinions in court.
Who is an Expert Witness?
A suspect using passive language like "the money disappeared" instead of "I took the money" is exhibiting a linguistic phenomenon known as this.
What is Psychological Distancing (or Pronoun Dropping)?
This formal, continuous log tracks every single person who handles, transfers, or inspects a piece of physical evidence from the crime scene to the courtroom.
What is the Chain of Custody?
In the 1932 Lindbergh kidnapping case, investigators noted the ransom note consistently placed the dollar sign after the number ($50.000$), pointing to a writer from this geographic region.
What is Europe (or Germany)?
In modern crime labs, this two-part analytical tool acts as the gold standard: the first part separates complex chemical mixtures, and the second breaks molecules apart to create a definitive molecular fingerprint.
What is GC-MS (Gas Chromatography-Mass Spectrometry)?
If a witness tries to testify about a rumor or repeat what someone else told them outside of the courtroom, the opposing attorney will object based on this legal rule.
What is Hearsay (or the Hearsay Rule)?
When speaking about a missing person, a suspect who prematurely switches from present tense ("she is") to past tense ("she was") before any body is found may be revealing guilty knowledge through a tense what?
What is a Tense Shift?
Gunshot residue (GSR), microscopic hair follicles, and soil particles transferred during a crime are classified under this specific subcategory of physical evidence
What is Trace Evidence?
During the JonBenét Ramsey investigation, the ransom note stood out as highly unusual to forensic examiners primarily due to this physical characteristic.
What is Unusual Length? (It was 2½ pages long).
Unlike most drugs, alcohol leaves the body at a steady, predictable rate, allowing toxicologists to do what with a blood test taken hours after a crash?
What is Estimate / Calculate the Earlier BAC (or Retrograde Extrapolation)?
Unlike unlimited challenges for cause, attorneys are granted a strictly limited number of these challenges to dismiss a juror without providing any reason.
What are Peremptory Challenges (or Peremptory Strikes)?
If an interviewer decides a suspect is guilty before the interview even starts and only pays attention to behaviors that seem suspicious, they are falling into this bias
What is Confirmation Bias?