Archive for the ‘Image Analysis’ Category

Reflecting back on 2009

When I think about the past year, and cases I’ve worked, training I’ve received, training I’ve given, there are a few things that stand out.

In the arena of cases, I had two unique experiences – A Daubert Hearing in 12/08, and Grand Jury testimony in mid-2009.

The Daubert Hearing was on image authentication (are the images real, and do they represent real people and real events). That hearing was U.S. v. Frabizio in December of 2008, and was one of the few Daubert Hearings on photography, imaging, or image authentication. It was an interesting case, as it was going to its third trial. I was retained by defense counsel to analyze and interpret the government expert’s report and findings. I provided information to the defense attorney on this report, and attended the Daubert hearing, and answered her questions on his testimony. With the limited number of Frye and Daubert hearings on forensic photography, forensic image analysis, or image authentication, it was an interesting experience to participate in this hearing.

The Grand Jury testimony was also on an image authentication case. In this instance, I was an expert witness for the government. I have testified in cases since the early 1990s, but this was my first time to testify before a Grand Jury. It was quite interesting, as there is no judge, no defense attorney, and the accused is not present, nor is a case detective. It’s the prosecutor, a court reporter, the members of the grand jury, and the witness. In this case, I was impressed by the professionalism of the prosecutor and the members of the grand jury – I can imagine a situation in which a system without the formality or presence of a judge, defense attorney, etc. moving toward chaotic – I was pleased that this was far from the case.

As to training I received, it would be a toss up between two classes I took in the field of photogrammetry. One was on reverse projection photogrammetry that I posted about earlier. The other was a class in using Photomodeler (a software application for applying photogrammetry) for close range photogrammetry, presented by Dan Mills of DCM Technical Services. Photogrammetry is taking measurements from photos, and there are several approaches to this technology. Unfortunately, there are very few classes available in close range photogrammetry or in reverse projection photogrammetry. I was fortunate to get excellent training in each in 2009.

Regarding training that I provided – it’s difficult to isolate any one specific workshop. But, I did have the opportunity to give four workshops in digital photography to the San Francisco Police Department in 2009. That agency purchased Nikon D700 cameras for their crime scene investigators and wanted each member to be trained in the use of that camera for crime scene and evidence photography. I was proud to be the trainer they chose to provide this instruction. We held four, three-day sessions, with eight investigators in each session. It was a pleasure to work with this agency and to see their dedication to providing their front-line personnel with the tools and training to do their job.

Lastly, another highlight of 2009 was being appointed chair of the Forensic Photography and Imaging Certification Board of the International Association for Identification. It is an honor to have been chosen to fill this position, and our board is working hard on several projects.

The last year was successful in many ways – looking back at a few of the highlights helps see where we are today and prepare for the future. I’m looking forward to more interesting cases and great training opportunities in the coming year.

G

Reverse Projection Photogrammetry

Nov 22nd, 2009 - Filed under: Blog, Image Analysis, Photography, Video Analysis

The Law Enforcement and Emergency Services Video Association (LEVA) held it’s annual conference this week. I was fortunate to attend the two day pre-conference workshop on reverse projection photogrammetry presented by Richard Vorder Bruegge, Walter Bruehs, and Chris Iber, all from the FBI Forensic Audio, Video, and Imaging Analysis Unit.

Reverse Projection Photogrammetry is used to measure objects in a photograph or video. It can be used to determine if an individual could be excluded or included as a suspect based on height. In addition to using this method to determine the height of an individual in an image, I have used this technique to determine the position of objects in relation to their surroundings (after the objects were removed), the distance of safety barriers in construction scenes (after the construction was completed and the barriers removed), the size of cracks in a sidewalk (after the sidewalk was repaired), etc. from photos of those scenes.

The workshop covered issues related to the methodology and foundations of this technique. Any forensic image analyst or forensic video analyst who hasn’t yet had the opportunity to take this workshop should do so. It has been offered at the LEVA conference for two or three years, and also at the IAI Annual Conference.

Using Photoshop and Bridge for On-Screen Comparisons

Nov 9th, 2009 - Filed under: Blog, Fingerprints, Image Analysis, Photoshop, Video Analysis

Someone recently posted a question on the CLPEX website regarding on-screen comparisons. This question was specifically about fingerprint comparisons, but the method is the same whether comparing prints, footwear, vehicles, etc.

The first step is to determine which images to use (or eliminate). I frequently use Adobe Bridge for this. I set up Bridge in the Filmstrip workspace. If I need to compare two or three images to decide which I will use for the final comparison, I select multiple images and use the loupe tool to compare details. The loupe tool provides a 100, 200, 400, or 800 percent magnification of a portion of each image in the Preview panel. Just click on an image in this panel to activate the loupe, click and drag it to move it, click it again to close it. You can display one loupe on each image in the Preview panel, as shown here:

This image shows two images in Bridge with the loupe tool.

This image shows two images in Bridge with the loupe tool.

Once the images are selected, they can be opened into Photoshop for comparison.

If the images are of the same resolution and approximately the same cropping, then they can be synchronized for zooming and scrolling. Do this by choosing the “Zoom all Windows” and “Scroll all Windows” in the options for the Zoom and Hand tools. Now, if you tile the images side-by-side, and zoom, both images will zoom; scroll one, and the other will scroll as well.

A new blank layer can be added to each image and marks can be made on that blank layer to indicate various features. Multiple layers can be used to better separate different categories of features, etc. With the Extended version of Photoshop CS3 or CS4, the Count tool can be used to mark features.

G

Certification in Forensic Photography and Imaging

Oct 26th, 2009 - Filed under: Certification, Image Analysis, Photography, Video Analysis

I frequently read Jim Hoerrick’s excellent blog, Forensic Photoshop. In his October 12 post, he brought up the issue of certification, and it prompted me to comment on that topic here.

One of Jim’s points is that some certifications are not based on real world issues, and the correct test answers may be wrong when applied to the real world. Jim also mentioned that what he’s heard related to the certifications of theĀ International Association for Identification (IAI) is positive.

As the Chair of the Forensic Photography and Imaging Certification Board for the IAI, I thought it would be important to discuss a bit of our process. We have two parts to our testing for certification – a written test and a practical test.

The written test is based on two texts, that is intended to show if the applicant has the general knowledge of photography and imaging to meet the standard set by the IAI for certification. Our board reviews the texts and the questions every year to attempt to keep the test relevant with current technology and appropriate for the topic of forensic photography and imaging.

The practical test currently includes ten assignments, and requires that the applicant competently complete each of the assignments to pass. These assignments are as closely molded to real world assignments as we can make them. We are currently reviewing the assignments and the wording of them so that they continue to represent real world assignments, and so that the assignments are as clear and explicit as possible.

Our board is always looking for input and I invite anyone with input to contact me at any time.

G