Criminal Justice and the Law
The Science in Forensic Science
• 1 Observe a problem or questioned evidence and collect
objective data
• 2 Consider a hypothesis or possible solution to the problem based
on observation, giving direction to the work plan. This step
inductive reasoning, experience and imagination.
• 3 Examine, test, and analyze to support or refute a hypothesis.
• 4 Use deductive reasoning to make a determination as to the
significance of the evidence.
• 5 Evaluate and verify all evidence. This step is especially critical
to a forensic scientist because someone’s liberty can depend on
the work. All possible errors must be stated. Consideration must
be given to standardization, reproducibility, validity, reliability,
and accuracy.
Civil Law vs Criminal Law
Civil law- law that deals with noncriminal
suits brought to protect or preserve a
civil or private right or matter
Criminal law- regulation and enforcement
of rights, setting acceptable limits of
conduct in society
Individual Rights
Guaranteed by the Bill of Rights
• The right to be presumed innocent until proven guilty
• The right not to be searched unreasonably, either on one’s
person or in one’s home
• The right not to be arrested without probable cause
• The right to unreasonable seizure of personal property
• The right against self incrimination
• The right to fair questioning by police
• The right to protection from physical harm throughout the
justice process
• The right to an attorney
• The right to trial by jury
• The right to know any charges against oneself
Individual Rights
Guaranteed by the Bill of Rights
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The right to cross examine prosecution witnesses
The right to speak and prevent witnesses
The right not to be tried again for the same crime
The right against cruel and unusual punishment
The right to due process
The right to a speedy trial
The right against excessive bail
The right against excessive fines
The right to be treated the same as others, regardless
of race, gender, religious preference, country of origin,
and other personal attributes
Miranda Rights
• The following is a minimal Miranda warning:
You have the right to remain silent. Anything you
say can and will be used against you in a court
of law. You have the right to speak to an
attorney, and to have an attorney present
during any questioning. If you cannot afford a
lawyer, one will be provided for you at the
government’s expense.
Types of Crimes
• Violation- any time a breach of a law has a taken
place
– Can be minor or major crimes
– Crimes are classified as infractions, misdemeanors,
or felonies
• Infractions- violation of a rule or law that is not punishable
by prison
• Misdemeanors- a minor crime, less than a felony.
– punishable by no more than one year in jail
– Fines usually range from $250 to $2500
• Felony- more serious crimes that carry stiffer penalties
– Punishable by more than 1 year to life in prison or even death
penalty
Steps in Pursuing Justice
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Crime is reported or discovered…. If crime observed by police officer then can go straight to
arrest.
Police arrive
Investigation by police
Processing of crime scene
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Search and processing of evidence
documentation
Suspect identified
Probable cause = situation in which a reasonable and prudent person, viewing the available
information, would conclude that a crime has been committed and that the suspect committed it
<<<<If probable cause…
• Arrest warrant obtained and booking
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Miranda Rights Read
Booking= a police procedure following arrest that records basic information about the suspect, a
photograph, and fingerprints and perhaps includes a lineup
Jail or Bail
Arraignment- the first act in a criminal proceeding, where the defendant where the defendant is
brought before the court to hear charges and enter a plea
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Usually within 72 hrs of arrest
Pleas can be guilty, not guilty, not guilty by reason of insanity, double jeopardy, or nolo contendere (no
contest- admit no guilt or innocence yet accept punishment as though he or she was guilty)
Steps in Pursuing Justice
For Felonies
For Misdemeanors
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Preliminary or evidentiary hearing
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No jury
Judge hears evidence against defendant
Right to cross examination and to produce
favorable evidence
Judge decides to proceed to trial or
dismiss or reduce charges due to
insufficient evidence
Some states may use grand jury
instead of preliminary hearing
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Grand jury consists of 16-23 individuals
sworn in to hear evidence
Only prosecutor presents evidence, no
cross examination
Jury decides by majority vote to indict or
not indict suspect
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Indict = formally accuse
Trial
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If convicted followed by sentencing
hearing and prison or probation
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Possible opportunity for appeal
if acquitted then released
Trial
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Conviction or acquittal
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If convicted sentencing
If acquitted then released
Facets of Guilt
To prove a case, the “MMO” must be established; it must be
shown that the suspect had:
Motive—person had a reason to do the crime (not necessary to prove in a
court of law)
Means—person had the ability to do the crime
Opportunity—person can be placed at the crime scene
Burden of Proof
• In US, a person is presumed innocent until
proven guilty
– Burden of proof is on prosecution in criminal court
cases
• If there is reasonable doubt that defendant committed
crime then jurors are instructed to vote not guilty
– Takes all 12 jury members to vote guilty to convict
– Only 50% of trials lead to conviction of defendent
– Only 25% of trials lead defendant serving a year or
more in jail/prison
Plea Bargaining
• Plea Bargaining- an agreement in which a
defendant pleads guilty to a lesser charge and
the prosecutor in return drops more serious
charges to avoid the cost and time of trial
– Can occur at many parts of the judicial process
– About 90% of criminal cases are plea bargained
Federal Rules for Evidence
• In order for scientific evidence to be admitted in a
court of law, it must be:
– Probative: actually proves something
– Material: addresses an issue that is relevant or significant to
the particular crime
• Hearsay- testimony given by a witness who relates
not what he or she heard, saw, or knows
personally, but what others have said
– Knowledge is dependent on credibility of the person who
first made the statement and is not considered reliable as it
is not taken under oath and does not allow for cross
examination.
– NOT ADMISSABLE in CRIMINAL TRIALS yet IS ADMISSABLE
in CIVIL SUITS
Admissability of Evidence
• The Frye Standard
From the 1923 case Frye v. United States
Scientific evidence is allowed into the
courtroom if it is generally accepted by the
relevant scientific community (particular field of
study.)
---The Frye standard does not offer any
guidance on reliability.
---The evidence is presented in the trial and
the jury decides whether it has significance
to the case or not.
Admissibility of Evidence
The Daubert Ruling- revision of Frye Standard
From the 1993 case Daubert v. Dow
• The judge decides if the evidence can be entered into the trial. Admissibility
is determined by:
1) Whether the theory or technique can be tested
2) Whether the science has been offered for peer review
3) Whether the rate of error is acceptable
4) Whether the method at issue enjoys widespread
5) Whether the theory or technique follows standards
• Helps keep junk science (pseudoscience) out of courtroom
• Federal Ruling yet states are expected to use
acceptance
Expert Witness
• Expert Witness- person specializing in a particular
techinical or scientific area of study
• The expert witness presents scientific evidence in
court. He/She will:
– Establish credibility through credentials, background experience.
– Evaluate evidence.
– Render an opinion about the evidence (whether or not it
incriminates defendant)
The court or judge may accept or reject the
opinion’s significance.
• Both prosecution and defense can present expert
witnesses