Expert Article Library
Common Questions Concerning Forensic Imaging
by Steve Cain
By Steve Cain Email: firstname.lastname@example.org
What is Forensic Video Image Analysis?
Forensic video image analysis is the relationship between video image processing, law enforcement, industrial security and the courts. It is a relatively new scientific tool for enhancement and identification of individuals and situations in recorded video crime scenes.
VCR tapes suffer noise, low light level environments, motion blur, and time base synchronization problems. Perpetrators are too small for identification and four camera scenes are compressed to a single frame, quad format. All these situations have been successfully resolved by forensic image processing techniques.
Low light level can be brightened. Small size regions containing the perpetrator can be magnified times two and times four with optical like clarity. Motion blur and time base distortions can be removed. Quad camera images in a single frame can be magnified to full camera views. Fields can be enlarged to frames. The same technique can remove perpetrator motion blur. License plate alphanumerics can be magnified and enhanced for legibility.
Are results from this type of analysis accepted by law enforcement and in a court of law?
Yes, there have been many cases where investigators have obtained positive identifications and arrests. Convictions have been obtained using this technology and public defenders have made practical use of this technology for their clients.
There are several court decisions that have allowed forensic video image enhancement into evidence.
Ø Roger Dolan v. State of Florida. an Affirming Appellate Court decision determining that computer enhancements were properly admitted.
Ø Nooner v. State the Arkansas Supreme Court held that where there is no evidence to indicate that the enhanced stills somehow changed a face, features, or physique, or were altered to include someone or something not present on the videotape, the stills were admissible.
Ø English v. State Georgias Court of Appeals compared the admissibility of computer-enlarged photographs from videotape to the use of photograph enlargements. Where the evidence establishes there is no distortion of the images on the original videotape, then the computer-enhanced photographic stills are admissible.
What process does a tape go through when it enters AFTI?
First, the tape is logged in by the office manager and all sides of the tape are scanned and put into the file so there is a record of the condition in which we received the tape. We check to make sure that the tape is write-protected and a copy is made as a back up.
The technician does an initial overview of the tape to make sure that instructions from the client are clear and that the scene or object to be enhanced is located and clearly understood. The length of the tape, record mode, time code, head switch, and cross pulse information are all noted in cases where authentication is an issue.