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Friday, June 28, 2019

Junk Science?

Great news from Texas has brought out a bunch of people with conflicting agendas. The great news? The George Powell case has moved to retrial after the Texas Court of Criminal Appeals vacated the conviction and ordered a new trial.

Whilst the media buzzes about the evidence used in the original trial, and throws "junk science" in the same sentence as "forensic video analysis," most in the media commit journalistic misconduct in their reporting of the case and the circumstances around the re-trial.

Take this article (link) for instance, "George Powell has maintained his innocence the entire time he's been behind bars. Now, he will have a chance to prove it."


In vacating the conviction, George Powell's status has returned to Innocent as the "proof" of his guilt has been vacated or struck down. Powell, under US law, is innocent until proven guilty in a court of law. As a presumed innocent man, he should be afforded the opportunity to make bail and to prepare for his defense.

When the trial begins, it's for the prosecution to offer the evidence that links Powell to the crime, if such evidence exists. It perverts the course of justice to require Powell to prove his innocence. Why? Not only is it the way our system works, innocent until proven guilty, but it's impossible to prove a negative.

Thus, when the trial begins, it's not "forensic science" that will be on trial. It's not "forensic video analysis" that will be on trial. What will be on trial is the evidence, offered up as proof of some condition. Then, it's up to the Trier of Fact to evaluate that evidence.

Forensic science and forensic video analysis are scientific, when performed scientifically by educated, trained, and proficient practitioners utilizing valid tools and an appropriate and valid methodology.

As regards Photogrammetry specifically, a measurement shouldn't be used to "identify" an object or a subject. Rare is the case that there is nominal resolution in the evidence item sufficient to measure with an output range that is so very precise. If the measurement's range of values in this case, properly employed, is between 5'6" and 5'10", as an example, then more than 65% of the population of the area will fit within that range. It's hardly an identifying characteristic. It does, however, help prioritize tips as well as to help exclude from the enquiry those subjects more than a standard deviation away from that range. This is why it's important to engage in valid methods when performing an analysis.

Tuesday, June 25, 2019

So you want to dive deep?

During last week's class, and at the request of several who wrote ahead to make sure that we were going to "dive deep," we dove deep into science. Here's an example of how deep the discussions often go:

In a modern chemistry textbook (link), students read the following:

"Matter comes in many forms. The fundamental building blocks of matter are atoms and molecules. These particles make up elements and compounds. An atom is the smallest unit of an element that maintains the chemical identity of that element. An element is a pure substance that cannot be broken down into simpler, stable substances and is made of one type of atom."

Sound good, so far? No, actually. There's so much missing.

For most people, this seems simple. The statements are matter-of-fact about how material objects exist.  We read them and assume that this has been seen and proven and when we look at a piece of wood or a drop of water, we tell ourselves that beyond the reach of our eyes, there is actually no “wood” or “water” but simply atoms arranged in different ways to cause different substances to appear to us, like an Impressionist painting composed of dots of paint.

If we move back, however, to the early 1900s, students were taught the following in The Elements of Chemistry: Inorganic and Organic. Norton, S.A. 1884 (link):

"We know nothing of the manner in which the ultimate particles of matter are arranged together: we believe that they are arranged in accordance with certain theories which we shall now proceed to develop.

All masses of matter may be subdivided into very small particles; but it is probable that there is a limit to this subdivision, and that all bodies are made up of particles so infinitesimally small that they are inappreciable to our senses. By the terms of this theory,

A molecule is the smallest particle of matter capable of existing in the free state:

An atom is the smallest particle of matter that is capable of entering into or existing in a state of chemical combination."

Notice how carefully the old teachers distinguished facts from theories.  The textbooks tells students plainly that scientists believe in theories and that teaching about atoms and molecules is a matter of faith not facts.

In this same textbook, Norton warns of errors that people are prone to when they speak of the science and its facts.  We read:

"The facts of chemistry are established by experiment, and are capable of being reproduced. They find a practical application in the arts, which is altogether independent of any explanation that may be made of them. When, however, we attempt to reason upon these facts, to classify them, to interpret them, we at once begin to form theories. A theory which renders a reasonable explanation of a great number of facts is useful (1) because it enables us to group them into a system, and (2) because it often leads to new experiments and to the discovery of other facts.

We are liable to three errors: (1) we may assume that to be a fact which has no existence; or (2) we may sometimes mistake a phenomenon, so as to imagine that to be a cause which is only an effect of some unknown cause; or, finally, (3) we may become so accustomed to the language of theory as to mistake its definitions for facts."

Can you  not see how different the mind of the student formed by this older textbook is than the modern textbook which commits the third error learned of?  Teaching of atoms and molecules, in modern textbooks, is no longer couched in terms of  theory and belief.  It is presented as immutable fact.  What is fact is that there is no more proof that atoms actually exist today than there was in 1900. The language of theory has simply been abandoned by modern scientists.

Swap out the word "chemistry" for "video analysis" or your specific forensic science discipline, Norton's caution still makes for great advice - from 1884.

This simple discussion, generic to science, has profound implications in the forensic sciences. I speak often of what we "know" vs. what we can "prove," of the null hypothesis, and of conducting valid experiments. Remember the NAS Report's conclusion in 2009 - forensic science sucks at science. Well, how does forensic science remedy the situation - by engaging in actual science. That all starts with understanding how science is conducted.

As relates to measurements, comparisons, vehicle determinations, and etc., we start with the basics. To get to a vehicle determination, we must first have a nominal resolution sufficient to address the task. Same with photogrammetry - we need sufficient nominal resolution of the item or object of interest so that the measure will (at least) exceed the error. We also must understand that a measurement can't be used to identify something. The measure only contributes to the classification of the item or the object.

So, if you want to dive deep - really deep - our classes are open to all who have an enquiring mind. Even our introductory courses move beyond simple button pushing to explore the depth of the discipline.

Friday, June 21, 2019

Practical Field Photogrammetry

Another successful Photogrammetry class is in the books. I'd like to share a few thoughts on the experience, as well as an example we worked on in one of the field exercises.

The old adage, "a poor workman blames his tools," is only part right. If you don't have the right tools to begin with, you'll be up against it. In the justice system, analysts are often stuck with what they've been provided - by the lowest bidder. This is something I realized years ago in that crime factory of a city that I used to work in. I needed a kit that was economical, rugged, portable, and easy to work with. It needed to be economical because the expense of kitting myself out was coming out of my own pocket.

As regards measurement exercises, I've seen many height charts / resolution charts on offer at trade shows and on-line. The ones in my price range were often printed on ink jet and when mounted, mounted on cardboard with a rigid frame. They were bulky and awkward. They maybe would last a month of regular use.

Having a background in art, working as a commercial artist and having run art departments in my youth, I decided to design and manufacture my own resolution chart.

Beginning with the end in mind, I decided to not go with the standard checkerboard style. I didn't want the black boxes to touch each other. At a distance, and given the massive compression on most surveillance systems, I wanted to avoid the bleed-over that often happens with the checkerboard designs. Take this from the Amped FIVE sample folder, as an example of the bleed-over.

This image is a close up, and in the camera is less than 12 feet from the chart. Still, you can see the problems of trying to establish the corners for an "eyeball" nominal resolution calculation.

The types of enquiries we often face deal with questions of license / registration plates at distances of 50'-250'. Take this example from class.

The camera is mounted on a light pole about 100' from the target, elevated about 12' from the road. I've processed it for display here in FIVE. The system is on the higher end of the generic black-box Chinese DVR spectrum and is well maintained. The owner of the system is a friend and the strip mall isn't that popular, so it's a nice place to have a field day.

My resolution chart is commercially printed on a PVC board. It's durable, water proof, and can stand propped up against the back of the car. Thus, I don't need to carry a stand or easel. It fits nicely behind the driver's seat of my truck.

Cropped in on the back of the car and the chart, this is the view at 100'. The left-most blocks are 2", the middle squares are 1", and the right-most squares are 1/2". There's very little bleed or compression artifacts around the 2" squares.

There are two stickers on the rear window. What's the diameter of the top sticker? I've got a good look at the 2" squares, so I can use those as my references. I can also use them to calculate the nominal resolution. If I use the Ruler in FIVE to measure the pixel length of the 2" squares, I get 4px.  Thus, the nominal resolution around the rear of the car is 2px/in.

Moving on to measurements of the items of interest on the vehicle, accurately selecting the X and Y axis in FIVE takes just a minute. The results are displayed in seconds. Things like stickers help to "individualize" the car and differentiate it from the other Honda Fits in the general area. This one has a 6" diameter round sticker on the center left of the rear hatch's window, above another sticker.

We can check our work by measuring an object of a known length.

US license plates are 12" long. This car appears to have a license plate frame. We measured from the outside of the frame on both sides. The results are again displayed. Assuming a bit of error (Measure 2D in FIVE does not compute error as 2D measure is simple planar geometry), at 100' from the camera and with compression, that's not a bad result - 1/2" frame width on both sides is not out of the realm of possibility.

What makes this possible? An easy to use resolution chart.

This is a simple example. But the technique is the same for your basic reverse projection photogrammetry experiment. Make a recording of the scene with the chart placed appropriately, then overlay the two recordings (that's the reverse projection part) in order to facilitate the measurement (that's the photogrammetry part). In this case, everything is roughly on the same plane, so I used FIVE's measure 2D. FIVE has 1D, 2D, and 3D measurement capabilities.

The last part of this exercise was the validation of the results. Validating results, in each and every case, is a must. There is no research out there that can be utilized that "globally" validates reverse projection photogrammetry. Every case is unique - different camera, different lens, different DVR, etc. Thus, you validate. The few text books out there that mention RP advise validating each case. In the SWGDE doc on photogrammetry (link), they advise the analyst to calculate / determine "... the accuracy and precision of this result." That's just another way of saying, "validate your results."

Keep in mind that if you're using a mixed-methods approach (laser scan point cloud + still CCTV frame), that method has never been validated outside of some analyst's casework. Remember, getting evidence and testimony accepted in one venue is not validation. So please, do your validations.

There's one more Photogrammetry class scheduled for 2019. You can check out the calendar of classes on offer here. This course tends to fill fast as there are no "non-vendor specific" courses on the subject of photogrammetry available in North America. It's a very intense week as we dive deep into the science and practice. It's a very tiring class to teach. It's a lot of information to transfer in a week's time. But, I enjoy it.

When students take this course, they've usually been through the LEVA levels and the various tool-specific training sessions. They're looking for more training, or topic-specific training. They're usually well kitted-out for the basic stuff. Thus, what do you get for the person who has everything? A squeeze ball and a few branded pens? No. Students get the digital printing file of the height chart and instructions on contacting the commercial printer we use. The cost of printing and shipping is usually less than the cost you'll find in the forensic magazines or at trade shows for their charts. If you can't make the class and would like the file, a small stipend is all it takes. If you'd like me to arrange the printing and have it shipped to you, the small stipend + the printing / shipping costs is still reasonable (I don't resell the printing/shipping). Either way, just send me a note and we'll get it set up for you.

Until then, have a great summer ...

Monday, June 17, 2019

Forensic Photogrammetric Analysis

This week, I'm happy to be teaching one of my favourite subjects, Photogrammetry.

Unlike the many tool-specific courses offered by the many vendors in the laser scanning space, the Forensic Photogrammetric Analysis course that I've been teaching for a while now focusses on the science of measurement as well as best practices that will help arrive at valid conclusions.

Here's a bit of a sample of what we're on about this week...

A few months ago, I wrote about calculating Nominal Resolution during the content triage stage of the image / video processing workflow. That critical process depends upon an accurate measurement of the distance from the camera to the object of interest. Who's responsibility is recording this measurement? Did you collect the video from the crime scene / witness location? If you did, did you roll out your tape measure or use your roller measuring wheel? If not, why not?

If not, might it be due to a lack of knowledge about the importance of calculating the nominal resolution? Perhaps you simply don't have the right kit.

You can buy your tools from a dedicated forensic science / crime scene vendor like Sirchie. Or, you can head over to your local home improvement store. At Home Depot, you can get a 300' measuring tape for under $40.

This Lufkin measuring tape is currently $38. A similar measuring tape from Sirchie is almost $80.

The same goes for a measuring wheel.

The Lufkin measuring wheel at Home Depot is less than $35. A similar model at Sirchie is over $70.

The point?

It doesn't have to break the bank to perform measurements at scenes that will later inform measurements within your images and videos.

If you'd like to know more, or if you'd like to sign up for our next class this fall, head over to our training page and see what's on offer. I hope to see you in class soon.

Tuesday, June 11, 2019

Retrieval / Seizure of Electronic Evidence from Crime Scenes

Twelve years ago, a few multimedia analysts got together via emails and phone calls to create a training class around an emerging topic - what to do with the video contained within these black boxes that folks were encountering at crime scenes.

Several of us had "figured it out." We figured out what worked in our own contexts. What worked for me in Los Angeles was slightly different than what worked in New York, or Virginia, or Texas.

We hashed out a loose curriculum for what was eventually delivered at the 2007 NaTIA conference in Pittsburgh. In that course, we presented a hands-on overview of the technology, the legal aspects, and ideas for procedures that could easily be implemented by state / local agencies.

This experience lead to the creation of the red flip book, aka Best Practices for the Retrieval of Video Evidence from Digital CCTV Systems. I'm quite proud of what we all accomplished in the production of that handy guide, which is still available from the CCTSO.

From there, the group was brought together again to create the curriculum for what would become the RECVR class at FLETC.

From that point, several of us went on to create separate versions of the essential materials, delivering it across the county (and the world). I've had the privilege of presenting this topic across the US and Canada, as well as in Pretoria, South Africa to the South African Police Service.

Whilst most classes need to choose a platform from which to work, and you'll need tools to perform essential work in restoration, clarification, and analysis, my curriculum has always attempted to offer a "non-platform specific" option to learners. I've presented as many tools as possible, many of them free / open source. I've focussed on policy, procedure, and workflow. I've split the topics around retrieval from the topics around seizure. I think the curriculum is rather comprehensive, yet accessible to learners of all types (novices - advanced analysts).

During my years with Amped, there was a lot of internal tension around those classes that I had previously designed and presented being offered by an Amped employee. Thus, they weren't. There was also a bit of angst about the way in which I presented the training around the Amped tools. I don't like simply focusing on buttons and functions. I try to contextualize the tools, and thus present the training in a way that builds competency.

So, with Amped's retreat, I'm happy to say that my full slate of classes is back on offer. You can find them on all listed by clicking hereRetrieval / Seizure of Electronic Evidence from Crime Scenes is back and better than ever. It doesn't really compete directly with the other classes out there. On the contrary, it's entirely complimentary.

You see, every instructor and curriculum developer has their own point of view and experiences. Each brings all of that to their courses. I'm no different in that respect. I don't usually toot my own horn, but this is different. My story helps frame the creation of the classes. Here it is:

  • I'm a Certified Audio/Video Forensic Analyst (AVFA). The process of investigating the three bodies that offer certification, honestly apprising the costs/benefits of each, deciding on a path, and carrying it out to completion has been an over-a-decade journey.
  • I'm the author of the best-selling book Forensic Photoshop (available on Amazon.com). Getting a book published isn't as easy as it seems. Ten years ago, it was a daunting task. Putting yourself out there for others to critique is an amazingly stressful ordeal. I'm glad that I did it.
  • I'm a co-author of Best Practices for the Retrieval of Video Evidence from Digital CCTV Systems (red flip book). Collaborating with an amazing group of international all-stars in the field, listening to their diverse views, creating, compromising, standing firm, and finally seeing one's work in printed form was an awesome experience.
  • When I retired from the LAPD, I had spent a third of my life in police service. Based on an 8 hour work day, and the amount of actual hours I had worked, I had worked 33 years worth of 8 hour days during that time. During the last half of my career,  I hardly saw my family and friends, my health suffered, and I was heading towards burn-out. Given the amount of crime in LA, and the relatively small size of my old group, a lot of the way in which I work and structure my courses comes from the "factory of crime" and the need to work efficiently in the face of constant requests for service. Also, my focus on human factors, taking care of one's self, and doing one's best to eliminate bias comes from this experience.
  • I currently serve the community on the Organization of Scientific Area Committees on Forensic Science (OSAC), Video / Image Technology and Analysis (VITAL), as the Video Task Group Chair. Last year, we moved the DCCTV Guide to an ASTM standard. This year, we're about ready to move the many SWG docs around forensic video analysis to a common ASTM standard.
All of this finds its way into my classes. I'm not just a talking head. I'm not just reading a script. I'm giving my honest assessment of the topic, and a helpful set of instructions to get the learner to mastery.

If you're ready to move beyond "button pushing," head over to Apex Partners to check out what's on offer. Sign up for a class or two. I hope to see you soon.

Friday, June 7, 2019

Forensic Science or Investigative Support

In 2015, then Deputy Attorney General Sally Quillian Yates announced that the Justice Department will, within the next five years, require DOJ-run forensic labs to obtain and maintain accreditation and require all department prosecutors to use accredited labs to process forensic evidence when practicable. Additionally, the department has decided to use its grant funding mechanisms to encourage other labs around the country to pursue accreditation.

If all that you read in the announcement was the headline and the first few paragraphs, you'd be left with the impression that the entirety of forensic science functions under the DOJ's control would be a part of this new initiative. You'd believe that ... and you'd be wrong.

In the fifth paragraph of the announcement was this, "The new policy does not apply to digital forensic labs. Instead, the Deputy Attorney General has asked the NCFS to develop separate recommendations on accrediting of labs that conduct digital forensic work, given the difference in the practices of forensic analysis of digital evidence."

This requires a question be asked, is the analysis of digital evidence a forensic science or investigative support function?

The FBI's FAVIAU is part of the Operations Technology Division. From their web site, "The world-class capabilities developed and deployed by the Operational Technology Division (OTD) have been instrumental in averting a terrorist plot, identifying adversaries involved in espionage activities, and helping to convict a child pornography subject. And these are just a few examples of where OTD has provided technical support in developing and deploying a capability in an FBI investigation or national security operation. OTD’s capabilities can be categorized into seven areas, all of which are used across the Bureau’s intelligence, national security, and law enforcement operations."

It seems that the FBI considers it's digital evidence labs to primarily serve an investigative support function, even though FAVIAU and the many RCFLs are fully functional and accredited forensic science laboratories. It's also worth noting that the digital evidence functions aren't part of the FBI's actual laboratory.

Similarly, the LAPD (my former employer), does not house it's digital evidence functions within its crime laboratory. My old unit (the Electronics Unit), is a part of the Technical Investigation Division, which is a part of the Detective Bureau.

"The Technical Laboratory is comprised of four specialized units that provide support services to investigative personnel in the Department - the Latent Print Unit, the Photographic Unit, the Polygraph Unit, and the Electronics Unit. Most Technical Laboratory personnel operate out of Piper Technical Center. Some field services operate out of the Van Nuys Community Police Station."

My old unit handles audio, video, and mobile device forensics - very similar to the coverage provided by the FBI's FAVIAU. Like the FBI, computers ("digital evidence") are handled by a separate unit. At the FBI, there's the CART team. At the LAPD, there's the Computer Crimes Unit. The LAPD also has several siloed digital evidence "labs" within sensitive / specialized units. I suspect the FBI does as well.

I know from my own career at the LAPD that it's entirely possible to "serve two masters," investigative support and forensic science. It's possible to work fast (investigative) and accurately (science). The modern toolset has helped tremendously.

But, within this seeming split, it's important to note that the other forensic science disciplines also serve this dual function. DNA results are used in investigations to rule in/out persons of interest. Same for latent print and firearms results.

So why the separation?

I think the separation has a lot to do with compliance / accreditation issues. The perception is out there that accrediting digital laboratories under ISO/IEC 17025 is complex and burdensome, and because accreditation groups like ANAB allow agencies to determine which aspects of its testing, calibration, and/or inspection services to accredit, that it's much easier to exclude digital forensic labs than to include them. In this case, perception is not reality. Accreditation of digital evidence labs is actually pretty straightforward.

If you'd like to know more, or if you're exploring accreditation for your lab, let me know. There's a clear path forward that many have taken. You're not alone. I can help.

Wednesday, June 5, 2019

I'm AVFA Certified

It's one thing to take a certification in some random Prometric testing center. It's quite another to get your certification package in the mail. Yay!

It was a pretty thick package. Certificate, ID card, membership info, program info, forms, and etc. Everything arrived in a week. That's pretty fast, considering the distance.

One of the interesting items was a set of forms for submitting my continuing education information annually. They do want to make sure that you're continuing to educate / train yourself within your chosen discipline. It's interesting in that they want the information annually, not 4 years later (oh, crap! I don't have enough CE's. What do I do now?!...)

In all, getting certified was a refreshingly pleasant experience. No drama. No stress. Very professional.

Now, it's back to work ... If you're interested, seats are still available at next month's Introduction to Forensic Multimedia Analysis with Amped FIVE course at our office in Henderson, NV.