Identifying and Collecting Physical Evidence

Law 120
To prove beyond a reasonable doubt that the accused was present at the
crime scene when the offence was committed, the collection, preservation
and analysis of physical evidence is a crucial aspect of police work.
Physical evidence – any object, impression or body element that can be
used to prove or disprove facts relating to an offence. This type of
evidence carries greater weight in court over witness statements.
Forensic evidence – application of biochemical and other scientific
techniques to criminal investigation.
Forensic scientists examine/analyze physical evidence found at a crime
scene. They do most of their work in labs but also spent a lot of time giving
expert testimony at trials and inquests. Some specialize in autopsies or
firearms. Others can determine a car driven by an accused by the paint
chip left at the scene.
The most frequently used tools in
the commission of crime are
hammers, screwdrivers, and crowbars. Often
these tools will have individual characteristics
on their surfaces or edges that can be
detected in crime laboratories. These marks
can be made either in the manufacturing of
the toll or by normal wear and tear.
Impressions are patterns or marks found on various surfaces,
caused by different objects such as fingers, gloves, shoes,
tires or tools. Collecting impression evidence is done in two
stages. First, the impression is recorded by photographing
or scanning it, or taking a mould. Then the police try to
match the impression with the object that made it, such as
matching a fingerprint lifted at the scene with a print taken
from a suspect.
 Impressions have two characteristics:
1. class characteristics – general attributes of an object such
as type, make, model, style and size. i.e. tires
2. individual characteristics – specific and unique features of
an object. i.e. specific wear and tear on a particular tire on
a particular car.
A fingerprint is a patterned mark left on a surface by a fingertip.
Prints can also be taken of a person’s hands, feet, or toes, but
fingerprints are easier to work with and classify. Because
fingerprint patterns never change and are unique to each
individual, a fingerprint is the best type of impression to use to
identify an offender. No two people have been ever found to
have the same exact fingerprint. Even identical twins have
different patters.
 There are two types of prints. A visible print can be observed by
the naked eye and is usually formed when the fingerprint is
coated in dirt, blood, grease or some other substance. This type
of print can be photographed immediately. A latent print, made
by the perspiration and oils that naturally form on the skin
surface, cannot be seen by the naked eye. This print has to be
‘developed’ to be photographed. Three methods are used to
develop latent prints.
prints on non-absorbent surfaces, such as metal and plastic,
can be dusted by using a graphite power that sticks to the
ridges of the print. The print is then lifted using adhesive
tape and placed on a white cardboard surface where it can
be photographed. The officer who lifted the print initials the
cardboard and it is stored for use later in court.
 The technique called ‘iodine fuming’ is used to lift prints
from absorbent surfaces such as paper and cloth. The area
being investigated is placed under iodine fumes; any existing
fingerprints absorb the iodine and become visible.
 A laser beam can be used to illuminate the print. Sweat
compounds deposited on the surface absorb the laser, and
the print turns yellow and can be photographed.
Gloves do not necessarily hide a criminal’s
fingerprints anymore. Police can use glove
impressions to identify a suspect in almost
the same way they use fingerprints. To make
a positive identification, they compare the
impression’s class characteristics with the
gloves of a suspect.
If the police can find four shoe prints – two right
and two left – they can learn a lot about a
suspect. These prints can help them determine
the suspect’s approximate height and weight,
any injuries he/she might have sustained
committing the crime, whether the suspect was
carrying anything and whether he/she was
walking or running. Tire impressions can help
investigators determine the type of tires, make
of car, and direction it was traveling when it
entered or left the crime scene.
The police may issue an appearance notice for
summary conviction offences, hybrid offences, and
less serious indictable offences. This document
names the offence with which the accused has been
charged. It also gives the time and place of the court
appearance. The officer must believe that the
accused will appear in court on the given date. The
accused must also sign the document and receive a
copy of the notice. The officer will then swear an
information before a judge or justice of the peace.
This document states that the officer believes on
reasonable grounds that the person named in the
appearance notice committed an offence.
For more serious indictable offences, the police will arrest the
suspect and take the suspect into custody. Arresting officers
identify themselves
advise the accused that he or she is under arrest
inform the accused of the right to a lawyer
inform the accused of the charges
The purpose of the arrest is to lay charges, preserve evidence and
prevent the accused from committing further offences. Any
officer can arrest without a warrant if there are reasonable
grounds to believe that someone committed an indictable
offence, is committing an indictable offence or summary offence,
or is about to commit an indictable offence. After the arrest the
officer must swear an information before a judge or justice of the
If the accused resists arrest, the police can use as much force
as is necessary to prevent an escape. The police are
criminally liable for the use of unnecessary force. In certain
circumstances, they can apply force that could cause death
or serious injury if it protects other from death or bodily
harm. In 1994, Parliament passed a law that gave the police
and anyone assisting them the power to use deadly force.
They can do so in the following situations:
 the behaviour of a suspect might cause serious harm or death to
 the suspect flees to escape arrest
 there is no alternative means to prevent escape
When an officer stops someone for questioning, that person
is being detained. People who are detained do not actually
have to answer questions unless they are in a specific
situation, such as a police spot check on a busy highway or
being placed under arrest. Detention should lead quickly to
arrest—otherwise, the person should be free to go. If a
police officer insists on questioning or searching a reluctant
individual, that person should immediately demand to see a
lawyer and write down the badge number of the officer and
the names of any witnesses. Citizens detained illegally may
sue the police for false arrest or detention or complain to the
police commission. A citizen is allowed to use as much for as
necessary to resist and illegal arrest or search. However, the
force used must be reasonable.
Someone charged with committing a crime has the right to be informed
promptly of the reason for arrest and the right to obtain a lawyer without
delay. The Supreme Court of Canada has ruled that this includes being
advised of the availability of a duty counsel (a lawyer on duty at the
court). The police must also inform the accused that legal aid is available if
that person cannot afford a lawyer. A request to contact a lawyer must be
honoured immediately. Anyone who has decided to hire a lawyer can
refuse to answer any further questions, except those necessary to
complete the charge, such as name, address, occupation and date of birth.
When people are read their rights, they must truly understand them. If
the accused is intoxicated, the police must wait until they sober. If the
accused cannot understand English or French, they must be read their
rights through an interpreter. Once they decide to contact a lawyer, they
must have access to a phone and must be allowed to talk privately to their
lawyer. They have the right to give up counsel and answer police
Police officers are responsible for their conduct
and behaviour when carrying out their duties. If
they break the rules of police conduct, they can
be charged under criminal law or sued under civil
law. Each province has a board that reviews
complaints from citizens concerning police
conduct. Police officers often have to make
quick decisions to save their own lives and those
of others. At all times, officers must act on
reasonable grounds using as much force as is
necessary for that purpose.
The accused does not have to take part in a line-up, where
several individuals, including the suspect, line up for
possible identification by the victims or witnesses. Nor
must the suspect take a polygraph test (lie detector test)
or give blood, urine, or breath samples (except in cases of
impaired driving offences). The police are allowed to
obtain DNA samples from a suspect but they must have a
warrant to do so. It actually might be to the suspect’s
advantage to permit evidence to be collected. For
example, when murder has been committed under the
influence of drugs or alcohol, the extent of the influence
might affect the outcome of the trial or even the sentence.
If the accused flees the scene of the crime, police can
swear an information before a judge/justice of the
peace. A document called a summons orders the
accused to appear in court at a certain time and place.
It is delivered to the accused by a sheriff or a deputy.
If the police can show a judge that the accused will not
appear in court voluntarily, the judge will issue a
warrant for arrest. It names/describes the accused,
lists the offence(s), and orders the arrest of the
accused. There must be reasonable grounds to
believe that the accused committed the offence.
Otherwise the judge will refuse to issue either the
summons or warrant.
Citizens can make arrests under certain
circumstances. This law gives store detectives,
private detectives, and other citizens the authority to
make arrests. The Criminal Code says that any one
may arrest a person who is committing an indictable
offence or who, on reasonable grounds, believes has
committed an indictable offence and is escaping from
or freshly pursued by lawful authority. The owner of a
property or an authorized person by the owner may
arrest anyone without a warrant who is committing a
criminal offence on or in relation to that property.
Informed and responsible citizens may want
to cooperate with the police. Innocent
persons often show their innocence by
immediately giving information to the police.
This can save time and money. Despite the
presumption of innocence, the police tend to
form conclusions based on an individual’s
behaviour when being questioned.
Once a person has been arrested, fingerprinted
and photographed, the police will often release
the accused until the trial. Release is usually
automatic for people accused of a summary
conviction or indictable offence that carries a
fine of $5000 or less. If the police believe the
accused will appear in court voluntarily and will
not commit and offences while awaiting trial,
the accused will sign a promise to appear. If the
accused does not appear on the assigned date,
the court will usually issue a bench warrant for
his/her arrest.
In some cases, the accused may be required to
sign a recognizance – a guarantee to appear in
court when required. A fine of up to $500 may
be levied if the accused fails to appear. Unless
the accused comes from another province or
lives more than 200km away, a deposit is not
usually required. The police may also request a
surety, someone who is willing to pay a certain
sum of money if the accused fails to appear at
trial. The surety also has to sign the
recognizance form.
Usually the police will try to keep suspects
accused of serious indictable offences in
custody after arrest. In such cases, the
accused has the right to make a bail
application. Bail is the temporary release of a
prisoner who posts a sum of money or other
security to guarantee his/her appearances in
court. A bail hearing must be held within 24
hours of an arrest, or if a magistrate is
unavailable, as soon as possible thereafter.
Section 11 of the Charter guarantees no one is to
be denied reasonable bail without cause. If the
Crown does not want the accused released
before trial, a show-cause hearing is held to
‘show cause’ and convince the judge that the
prisoner should stay in jail until the trial date.
“Cause” includes reason to suspect the accused
may flee; concern that releasing the accused
may be a threat to the safety and protection of
the public, or any other just cause. If the Crown
is successful, the judge will issue a detention
order to keep the accused in jail.
Some circumstances may justify a reverse onus, which means
that the burden of proofs shifts; rather than the Crown having to
show cause that the accused should be imprisoned, it is up to the
defense to show cause why bail should be granted. This happens
The accused is charged with committing an indictable offence
while already out on bail
offence is indictable and the accused is not a Canadian citizen
The charge involves failure to appear or breach of a bail condition
The accused is charged with importing, trafficking, or possession
for the purpose of trafficking narcotics (or conspiracy to commit
any of these crimes).
If the accused falls into one of these categories, bail will be
denied unless the accused convinces the judge that he/she will
attend court as required, not commit a crime while out on bail,
and not interfere with the administration of justice in any way.
If an accused person who has been arrested and
denied bail believes that he or she has been illegally
detained, that person can file a writ of habeas corpus
to appeal the court’s refusal to a higher court.
A writ of habeas corpus requires the Crown to produce
the detained person in court and then give reasons to
justify keeping this person in custody after trial. It
also requires the Crown to show that the prisoner is
not being mistreated in any way. If the Crown cannot
justify the continued detention of the prisoner to the
higher court’s satisfaction, the court may order the
prisoner to be released until trial.