I was recently interviewed by CTV News regarding the role surveillance video evidence will play in identifying suspects in the Boston marathon bombing that occurred on April 15th 2013:

CTV News Interview – Boston Bombing: Commentary by David McKay on Forensic Video Evidence 

There is no doubt in my mind that the suspect or suspects have been caught on camera at some point during the event or in the hours, days, or weeks leading up to the incident.  The question will be sifting through the thousands of hours of video and photographic evidence in order to identify the perpetrators.  One of the biggest issues the police and FBI will have to deal with is the massive amounts of digital information they will need to manage.  It will be a daunting task to get the word out to the public, so whomever may have that crucial piece of visual evidence can turn it over to the authorities in a timely manner.  It’s definitely possible that someone has taken a picture of the suspect on their camera and doesn’t even realize it yet.

Although the images and video that were taken right before and right after the bombing may be of critical importance, what may turn out to be even more crucial is the footage that has been recorded by all the surrounding CCTV systems leading up to the event in question.  It will be imperative for the authorities to work with the business community to ensure that any video data contained on CCTV systems in the area is protected from being overwritten in case this information is required down the road.  At this point in the investigation, it is too early to determine the extent of the recordings that may be required.  This will all be fleshed out over the coming weeks as the investigation starts to take shape.

The authorities may look to the approach that was used in the recent 2011 Vancouver Stanley Cup Riots to catalogue the evidence; however there are a lot of differences between this incident and what happened in Boston.  While it may be important to go through the “tagging” procedure that was used in Vancouver to create a searchable database of suspects, in the Boston circumstance this technique won’t be as effective or efficient since identifying a suspect needs to be done in a timely manner.  In Vancouver individuals were tagged based on characteristics in the hopes they may show up later in other sources of video, increasing the chance of identification and linking together that individuals activities.  In Vancouver, there was a finite time frame of 5 or 6 hours that could be focused on and perpetrators were carrying out their crimes overtly.  In Boston, the window of pertinent video evidence could stretch back weeks.  In addition, the perpetrators will be harder to recognize, since you can bet they will be trying to do their best to blend into the crowd.  I don’t think it is any coincidence that one of the devices was concealed in a black backpack – which just happens to be the most common colour of backpack carried by males.

There may be aspects of the Stanley Cup Riot investigation that can be used, but no doubt a more dynamic approach will need to be applied in this case.  The situation is more complex, and this will call for an equally complex approach.  I surmise that investigators will be focused on using the video evidence to piece together where particular parts of the explosive device or other debris may have travelled, which may shed light on trajectory, velocity, and direction.  Depending on what information is available, video recordings may assist the investigators in trying to determine the force of the blast by using frame rates and the distance travelled by particular objects to calculate velocity.  Furthermore a comparison of images before and immediately after the event will go a long way in assisting investigators to determine any inconsistencies and/or objects or individuals out of place right before the blast.  In any event, the video evidence will be crucial to the investigation, and there will be many more forensic details beyond identification of suspects that will hopefully be mined from the massive amount of visual evidence that exists.