Types of Evidence

Evidence can be uncovered in crime scenes or derived from testimonials.  The two most common types of evidence are testimonial and physical.

Testimonial - are statements from victims or witnesses of a crime

Physical - is real evidence based on actual fingerprints, hairs, fiber or materials obtained from the criminal or suspect at the scene of a crime.

When a crime is committed and the assailant has not been caught, evidence becomes necessary.  This is known as the "Locard's Exchange Principle."  This principle states that whenever a person enters an environment or place of business, something is added and something is removed.  In other words, everyone leaves behind evidence or a trace of evidence.

Examples of Crime Scene Evidence:

• Blood
• Fingerprints
• Hair
• Drugs
• Weapons
• Shoe prints
• Clothes
• Tape

These types of evidence left behind at the scene of a crime usually tell a story.  When physical evidence is analyzed and investigated properly, it can correspond with testimonial evidence.  Physical evidence is objective and can give authorities the proper channels to go through to handle a case.  Testimonial evidence is more subjective and can send authorities and investigators on wild goose chases if the source in which the information is derived isn't credible.

Someone giving their personal account to a crime can sometimes have an altered perception as to when the events occurred.  Testimony involving inaccurate stories, details and memory leave many criminal cases unsolved every year.  Physical evidence can be documented, collected and preserved and still hold up in a court of law.  Physical evidence that can break a case becomes known as the "silent witness." 

Physical evidence is a type of evidence that makes a crime investigation successful.  The collection of evidence such as impression marks, sharp objects, or fingerprints can bring all missing pieces together. 

Types of Physical Evidence

One of the most significant types of evidence is fingerprints.  The ability to obtain a fingerprint at a crime scene has made individualizing evidence possible.  Because no two individuals can have the same fingerprint, it is one of the easiest way to bring justice to a criminal case.  Fingerprints can be analyzed in a database with criminal fingerprints already on file.  If a match is made, then a criminal can be charged. 

Deoxyribonucleic acid (DNA) evidence, however, in many ways is becoming more important or just as important as fingerprint evidence.  It is the master molecule of every cell.  Because DNA evidence can take weeks or months to analyze and can be very expensive, it isn't used in every criminal case.  DNA evidence is not as easy to come by as "CSI" makes it out to be on TV.

DNA evidence was used to identify many of the September 11th victims.  When the World Trade Center site was under attack, there was no sophisticated evidence to identify more than 500 victims at one time.  The National Institutes of Health and other institutions used DNA profiling.  In addition to receiving 20,000 pieces of human remains from the disaster site, a database of the victims' DNA profile was used.  Out of the 2,792 people known to have perished, only 1,585 remains were identified by DNA extraction methods.

When it comes to understanding the different types of evidence uncovered at a crime scene, the more evidence collected, the greater the chance of conviction.  Another subset of physical evidence is trace evidence.  Trace evidence is evidence so small it may not be enough to measure.  With use of a microscope or ultraviolet light, trace evidence can be uncovered.  It consists of trace amounts of blood found on any object.  It can be extracted from morsels of dirt on a pair of shoes to wood splinters from a bullet hole.

Biological evidence is a little different.  It consists of bodily fluid or tissue.  Through DNA testing, biological evidence can provide a positive identification of any blood type.  Biological evidence consists of bodily fluids such as, blood, semen, skin, saliva, hair or bone. 

Other Types of Evidence

Crime scene investigations consists of a variety of other types of evidence that may not fit into the same categories.  With use of toxicology reports, investigators can determine what type of substances were in a person before and at the time of the crime.  Blood spatter or bullet trajectories are often uncovered with hope to reconstruct the crime scene. 

The different kinds of evidence are a perennial source of confusion. The character of truthfulness from any witness is placed in issue when he or she testifies.  Even if a statement is found to be hearsay, it may be admissible.  The federal rules contain at least 27 explicit hearsay rules.  Only a few may be used when the declarant is unavailable, but the remaining 24 are always unavailable.  According to federal rules evidence 801 (d), some kinds of hearsay statements are arbitrarily defined as nonhearsay. 

As stated earlier, many types of evidence can be used to help break a case but not all evidence can hold up in a court of law.  There are 24 hours in a day and some evidence may need to meet certain requirements in order for it to be reliable.  This happens when a person who is using testimonial evidence and suddenly cannot remember or his or her story doesn't corroborate the original testimony.  Depending on how circumstantial the evidence is, this may hinder a case or prolong it.

The main objective of evidence is to establish that proof has not been changed or altered before or during trial.  If there is any question from the events leading up to trial about the location of an item or evidence, the times and locations in which the event occurred, and who the witnesses really are, then the evidence cannot be accounted for.  In this case, evidence can be excluded unless another form of proof is available to support it. There is no way to make sure evidence will be found at a crime scene but when it comes to having solid proof, the best evidence in a case is physical.