74 Terms on File
The Case File Glossary
The vocabulary of the case file — forensics, investigation, and the courtroom, explained the way we use them on the show. Straight definitions, zero mystique.
01
Forensics & Evidence
- Locard's Exchange Principle
- The foundation of forensic science: every contact between two objects leaves a trace. A perpetrator brings something to a scene and takes something away.
- Chain of Custody
- The documented, unbroken record of who handled a piece of evidence, when, and why. A gap can get the evidence excluded at trial.
- Touch DNA
- Skin cells transferred by handling an object. Powerful but controversial — a few cells can travel on a handshake and land where their owner never was.
- CODIS
- The FBI's Combined DNA Index System, linking DNA profiles across local, state, and national databases.
- Forensic Genetic Genealogy
- Identifying suspects by matching crime-scene DNA to distant relatives in public genealogy databases, then building the family tree inward.
- Mitochondrial DNA
- DNA inherited only through the maternal line. Survives in degraded remains where nuclear DNA doesn't — common in cold case identifications.
- DNA Phenotyping
- Predicting physical traits — ancestry, eye color, hair color — from DNA alone, often used to generate suspect composites.
- Latent Print
- A fingerprint invisible to the naked eye, developed with powder, chemicals, or light sources.
- Ballistics
- The analysis of firearms, ammunition, and toolmarks — matching a bullet or casing to the weapon that fired it.
- Gunshot Residue (GSR)
- Microscopic particles expelled when a firearm is discharged. Presence suggests proximity to a shooting; absence proves little.
- Luminol
- A chemical that fluoresces on contact with the iron in hemoglobin, revealing cleaned or invisible bloodstains. It points — it doesn't prove.
- Bloodstain Pattern Analysis
- Reading the size, shape, and distribution of bloodstains to reconstruct events. Admissible but heavily contested science.
- Autopsy
- The medical examination of a body after death to establish cause and manner of death.
- Cause of Death
- The specific injury or disease that ended a life — for example, asphyxiation or a gunshot wound.
- Manner of Death
- The classification of how the cause arose: natural, accident, suicide, homicide, or undetermined.
- Rigor Mortis
- Post-mortem muscle stiffening, beginning within hours and fully set around twelve — one of several clocks used to estimate time of death.
- Livor Mortis
- The settling of blood after death, staining the lowest parts of the body. Fixed lividity can show a body was moved.
- Forensic Entomology
- Using insect evidence — species and life stage — to estimate how long a body has been where it was found.
- Forensic Odontology
- Dental identification of remains, and the now-discredited practice of bite mark matching.
- Isotope Analysis
- Chemistry that reads bones, teeth, and hair to reconstruct where a person lived and what they ate — a tool for identifying unknown remains.
- Trace Evidence
- Small transferred materials — fibers, hair, paint, glass, soil — that link people, places, and objects.
- Exemplar
- A known sample — handwriting, DNA, prints — collected from a person for comparison against evidence.
- Cold Hit
- A database match that identifies a suspect with no prior connection to the investigation.
02
Investigation
- Person of Interest
- Someone investigators want to talk to. Not an accusation — a step below suspect.
- Suspect
- A person investigators believe may have committed the crime, based on evidence.
- Modus Operandi (M.O.)
- An offender's method of committing crime — learned behavior that can evolve over time.
- Signature
- What an offender does beyond what's necessary to commit the crime — the psychological fingerprint that stays constant while an M.O. changes.
- Staging
- Deliberately altering a crime scene to mislead investigators — making a homicide look like a burglary gone wrong, for instance.
- Victimology
- The study of the victim — routines, relationships, risk factors — to understand why they were targeted and by whom.
- Canvass
- Systematic door-to-door interviews around a crime scene, hunting for witnesses and cameras.
- BOLO
- 'Be on the lookout' — an alert to law enforcement describing a person or vehicle of interest.
- AMBER Alert
- The public emergency alert for abducted children in credible, imminent danger — named for Amber Hagerman.
- NamUs
- The National Missing and Unidentified Persons System — the public database that matches missing persons cases to unidentified remains.
- ViCAP
- The FBI's Violent Criminal Apprehension Program, linking violent crimes across jurisdictions by behavioral and physical details.
- Profiling
- Inferring offender characteristics from crime scene behavior. A lead-generating tool, not evidence.
- The First 48
- The investigative truism that solve rates drop sharply after the first two days — evidence degrades, memories fade, trails cool.
- Cold Case
- An unsolved case no longer under active investigation, kept open pending new leads or technology.
- Exhumation
- The court-ordered removal of buried remains for new examination.
- Jurisdiction
- Which agency owns a case — a frequent source of friction and, in serial cases, missed connections.
- Task Force
- A multi-agency team assembled for one investigation, pooling jurisdiction and resources.
- Tip Line
- The public's channel into an investigation. High noise, occasionally the whole case.
- Geofence Warrant
- A court order for data on every device inside an area during a time window — powerful and constitutionally contested.
- Cell Tower Ping
- A phone's contact with a tower, placing it in a general area — not a precise location, whatever TV says.
03
Courts & Law
- Probable Cause
- The legal threshold for arrests and warrants: enough facts for a reasonable person to believe a crime occurred.
- Miranda Rights
- The warnings required before custodial interrogation — silence and counsel. Unwarned statements risk suppression.
- Indictment
- A grand jury's formal accusation, moving a case toward trial.
- Grand Jury
- Citizens who review the prosecution's evidence in secret and decide whether charges proceed. They indict; they don't convict.
- Arraignment
- The first court appearance: charges read, plea entered, bail argued.
- Plea Bargain
- Resolving a case by agreement — a plea in exchange for reduced charges or sentence. How most criminal cases actually end.
- Alford Plea
- A guilty plea in which the defendant maintains innocence while conceding the evidence would convict.
- No Contest (Nolo Contendere)
- Accepting conviction without admitting guilt — often to limit exposure in a civil suit.
- Beyond a Reasonable Doubt
- The criminal standard of proof — the highest in the legal system.
- Circumstantial Evidence
- Evidence requiring an inference — fully legitimate, routinely conviction-grade, and routinely misunderstood.
- Direct Evidence
- Evidence that proves a fact without inference — an eyewitness, a confession, a recording.
- Hearsay
- An out-of-court statement offered for its truth. Generally inadmissible, with a long list of exceptions.
- Exculpatory Evidence
- Evidence favorable to the defendant. Prosecutors must disclose it — that's Brady.
- Brady Violation
- The state's failure to turn over exculpatory evidence — grounds for reversal.
- Double Jeopardy
- The constitutional bar on retrying an acquitted defendant for the same offense.
- Statute of Limitations
- The deadline for filing charges. Murder almost never has one.
- Change of Venue
- Moving a trial when local publicity makes a fair jury impossible.
- Voir Dire
- Jury selection — the questioning that surfaces bias before a juror is seated.
- Sequestration
- Isolating a jury from outside information during trial or deliberation.
- Hung Jury
- A jury that cannot reach unanimity, ending in mistrial. The state may retry.
- Mistrial
- A trial terminated without verdict — for a hung jury, misconduct, or prejudicial error.
- Acquittal
- A not-guilty verdict. Not a declaration of innocence — a finding that proof fell short.
- Exoneration
- The formal clearing of a convicted person, often years later, by new evidence.
- Habeas Corpus
- The post-conviction challenge to unlawful detention — the vehicle for many innocence claims.
- Life Without Parole (LWOP)
- A life sentence with no possibility of release — in practice, the alternative to capital punishment.
- Insanity Defense
- The claim that mental disease prevented understanding the act or its wrongfulness. Rarely raised, more rarely successful.
- Competency to Stand Trial
- Whether a defendant can understand proceedings and assist counsel now — a different question from insanity at the time of the offense.
- Extradition
- The formal transfer of a suspect between states or countries — and why some fugitives choose their refuge carefully.
- Jailhouse Informant
- An incarcerated witness trading testimony for benefit. A leading cause of wrongful convictions.
- Wrongful Conviction
- A conviction of the innocent — driven by misidentification, false confession, flawed forensics, and misconduct.
- False Confession
- An innocent person's admission of guilt — produced by coercion, exhaustion, youth, or suggestion. It happens far more than intuition allows.