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Object and Face Recognition >> Content Detail



Lecture Notes



Lecture Notes

Here is an example of a lecture note for a class with a guest lecturer. It indicates the kind of relevant questions students must ask in class.
Guest Presenter

Officer Jack Skinner, Concord Police Department, police sketch artist.

Questions

What aspects of a face does a sketch artist pay attention to?
What face recall systems exist?
What are the potential limitations of face recall systems?

Brief Biography

29 years at Concord, last 6 years working as a police composite artist.
Does character sketches for retirements, police cartoonist.
Interest in art and police work.
Attended the Northeastern School of Criminal Justice.
Has taken various police composite artist courses, including a 3-week facial forensics course at the FBI academy.

What is a Composite Sketch?

Graphic rendering of the victim’s (or witnesses’) memory, get the emotions of the witness captured in the image.
Tool for the detective, not used for convictions. Occasionally, sketches are brought in to court, but they are considered hearsay evidence.
Useful for identification purposes or elimination of suspects.
Sketch is only as good as the witness.
Starting point on paper. The next step would be a photo lineup of similar-looking people.

Time

Unless the crime is traumatic enough, the memory will fade.
Except very traumatic events: for example, in rape cases, standard to wait 24-48 hours.
If the witness saw the perpetrator for a longer period of time, have more time to formulate image and give better, more accurate descriptions than if just saw briefly.

For what kind of Cases are the Services of a Police Artists Requested?

Big cases – when the Boston Globe asks questions like “What have you been doing on the case?” they can answer that they’ve got a police artist working.
High priority crimes, such as murder.

Sketch Ratings

Word question carefully. e.g. Can the officer pick the person out of a crowd with this picture? vs. How good is this? Try to remind witness this is their picture so they don’t try to just please the artist.
Occasional correlation between the rating and the apprehended person – high rating usually a pretty good likeness of the perpetrator.

Sketches have been used for a very long time. From Jack the Ripper to the Lindbergh kidnappers to Tim McVeigh.

FBI claims for the rank of most recognizable features:
1. Eyes
2. Hair
3. Nose
4. Head shape

Personal experience- head shape is the most recognizable.
Least recognizable features: ears.

Witnesses

Best witness is not always the victim, who may be too flustered or traumatized by the event.
With multiple witnesses, figure out who would be the best witness and draw their description. Then, starting with that image, get opinions of the other witnesses.
Best to interview multiple witnesses separately- could have problem of one being more dominant than others if they’re all in the same room.

Police Composite Artist is Also an Interviewer.

“cognitive interview” – witness talks, you listen.
Generally don’t sit across from witness.
Must relax the witness, make them comfortable.
Word questions carefully, ask open-ended questions so as not to lead the witness.
No pictures in the background, few distractions.
Bring victim mentally back to the scene Have victim sketch the scene. If possible, bring back to actual scene.
Let victim give the information rather than ask for it.
Be flexible with witness.
Don’t stop or interrupt.
Stay in particular descriptive regions (e.g. eye area).

Process

2 phases

Start with fact sheet.
Ask “If you saw this person again, could you identify him?”- if no, then no point in going on with sketch.
Ask “Does person remind you of anyone?”

Show pictures of various features (e.g. chin shape, nose type, face shape, etc).
FBI face book contains frontal male features from mugshots and pictures of FBI workers. Currently trying to get a female face book as well.
If anything looks similar, point it out.
Start with head shape.

Frontal Images

Images in FBI face book all frontal.
Most sketches are frontal, but there have been a few side views.

Computer Programs

Faces
Mac-i-Mug (?)

Personal Experience Involving Class Differences

Females more difficult to draw.
Women better at describing- may involve application of makeup.
Young (13-14 year olds) better than adults.

Yuri’s Mugger

Sketch evolved during the interview.
Hair changes, rounded out face, make the face look younger, nicer, deeper eye sockets, added smirk.
Second witness description as well.
Yuri: something was slightly off, but had already described all the features possible.



 



 








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