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Types of Evidence. Direct Evidence. Firsthand observations made by an eyewitness Can be used in court to prove a fact Eyewitness Eyewitness is a person who directly observes an event Police collect their names, addresses, and phone numbers
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Direct Evidence • Firsthand observations made by an eyewitness • Can be used in court to prove a fact • Eyewitness • Eyewitness is a person who directly observes an event • Police collect their names, addresses, and phone numbers • Some give accurate descriptions of what they saw or heard but some are not always reliable
Problems with Direct Evidence • The descriptions eyewitness give at a the scene may not match • People’s physical abilities, experiences, and emotions can affect their observations. They may be too scared or angry to notice anything. • Witnesses may be asked to recall events weeks or months after they happened.
The Lineup • A witness views the lineup through a one-way mirror so the suspect can’t see the witness. • Sometimes a person may be asked to step forward or repeat words the witness recalls hearing • Lineups are good when there is a likely suspect. All individuals in the lineup must be similar in appearance • Most witnesses assume the suspect is in the line up
Mug Shots • Photos taken when a person is arrested • They are taken from the front & side
Making Sketches • A forensic artist will interview witnesses and draw a sketch • More recently artists can use software to draw their sketches. The process becomes faster. • The software is a kit that contains a library of facial features, so the artist and witness can work together to build a reliable portrait.
Surveillance Cameras • These cameras record all action. • Sometimes the images are gray and blurry so it might be hard to match the images with an actual suspect’s face • In large places there may be many surveillance cameras. One person can sit in a room and watch what is happening throughout the location.
Facial Recognition Software • Software that can match a video image to an image in a database of mug shots. • It measures the distances between facial features on the video and them searches for mug shots with similar measurements. • The software can search up to 60 million images a minute.
Physical Evidence • Any object that can be used to prove that a fact is true. • Knife • Scrap of paper • Hair • Some physical evidence is found at crime scene but sometimes it can be found at other locations related to the crime.
Transfer of Evidence • Everywhere you go you leave a bit of yourself. • You also transfer materials from one place to another (ie track mud from yard into your house on your shoes or sand from the beach in your bathing suit)
Locard’s Principle • Every contact leaves a trace. • There is always a transfer of physical evidence at a crime scene no matter how careful criminals are. (hair = 100/day; 50,000 flakes of skin/minute) • They always carry away physical evidence from the crime scene too