Recap #CrimeChat Sept 16, 2013

Hands typing on a keyboard - drawingRecap #CrimeChat Sept 16, 2013. Today’s #CrimeChat was about real CSI. Retrieving DNA from certain surfaces can be done by swabbing and taping but those methods may not work 100% on porous surfaces, brick, concrete or, wet surfaces.

The M-Vac is a wet-vacuum sampling system. Jared Bradley, tweeting as mvacsys, said: “think of a medical grade carpet cleaning attachment that you would use for upholstery.”

Here is a clip to make this even more visual!

The solution they use penetrates into fabric or into a brick/rock but not more than about one centimeter. Then, the vacuum is set into motion, the fluids retrieved, and separated in the lab. The amounts to retrieve are unlimited. If the first collection bottle is filled you can put another one on the system and keep going.

dna vacuumThe M-Vac was invented by Dr Bruce Bradley, a microbiologist who ran a small service lab in Southern Idaho. Bruce was Jared’s father. Bruce passed away in 2009.

The M-Vac can be used in cases of assault where swabbing and taping did not render any results. One of those cases is described here. There is also a gang-related homicide case description here.

The beauty of this system is that it can be used to help advance cold cases. However, it can also test pre-conviction evidence in wrongful conviction cases and help address miscarriages of justice.

I asked Jared what kind of surfaces can be vacuumed. He said any surface, including stainless steel, plastic, rough masonite, carpet, floor tiles, product surfaces, fabric, animal hides, vegetable and meat surfaces, and many others. It can scan meat for e-coli and fruit for salmonella!

David Swinson wanted to know what primary agencies were using the M-Vac System. Jared said that amongst others police in the Salt Lake area have the system. Also, South Africa Police Services is using the system, but others – Mexico, UK, China, Russia etc – have distributors in the region so they will have access to it soon but have not officially started using it yet.

The costs of the device are about $15000 and then the costs ranges from $55-85 per sample. It is a portable system of about 65 lbs but it can be pulled around like a suitcase.

Jared explained that there is a university looking into DNA recovery from firearms and ammunition. I asked what the possibilities were for gun oil and residue in forensic arson detection cases. Jared thought that was interesting! As long as the evidence is not affected by being suspended in solution it just might work! He called it a good opportunity for research so if you see the M-Vac in arson detection cases … you heard it here first!

The latest in DNA recovery is not just of interest for law enforcement but also for authors! Use it in your mystery books. Exonerate a prisoners whose pre-conviction evidence was treated with the M-Vac. Now that I think about it, would love to use the M-Vac on Eunice Edwards-Zeigler‘s coat to find out whose blood was dripped on her jacket lapels. But I do not think that this would ever be possible. That case is from 1975 and what was once there might have deteriorated beyond testing. Maybe not in the Zeigler case but this is something to watch for and use in other cases.

MSI’s website is here. Jared will answer any questions you may have. just leave them in the comment box and I will let him know.




  1. Alice, overall looks great!

    On the Zeigler’s coat – if the coat has been maintained in a dry and cool area then the DNA material should still be there, so I wouldn’t hesitate to at least try the M-Vac on it!

    I think that’s it! Thanks again for the opportunity!


  2. Hi Alice,

    It was a fantastic #crimechat and great to be able to bring wider attention to this new technique. I asked a couple of questions in the chat that Jared probably missed because he was totally inundated, so I thought I’d mention them here in more detail.

    I’m particularly interested in the mixtures of DNA that have been obtained from the samples recovered by M-Vac. In the type of cases I’ve dealt with previously, especially those where we might be looking for low levels of DNA deposited by touch or handling, then DNA mixtures can be problematic. If they are low level, then they may be very difficult to interpret or of limited evidential significance. Sometimes we are faced with mixtures where a particular suspect can’t be excluded as having contributed, but that doesn’t necessarily mean that we can say with any certainty that the findings support that their DNA is present. I have written about the limitations of DNA interpretation on DCC before, and the issues are the same.

    I was interested to hear that in the gang-related homicide case mentioned in the chat, DNA mixtures were obtained in which clear major profiles were distinguishable, in comparison to the poor low level mixtures that had been previously obtained from the results of swabbing. I wondered therefore, if any other validation work has been carried out on samples under controlled conditions to directly examine the differences in mixtures obtained from the M-Vac versus other techniques. The Boston University work Jared highlighted during the chat shows an increased yield of single source DNA, but if improved mixture resolution could also be demonstrated under controlled validation conditions in addition to casework examples, then that would be a real selling point to the current UK forensic market.

    I was also curious about the consumables used by the M-Vac. Are the filters and any other consumables manufactured by M-Vac themselves or are they available from various suppliers? In either case, what measures are taken to ensure that consumables are DNA free?

    Thanks to you, Jared, and the other contributors, for another great #crimechat.

    Best regards,

  3. Sue,
    Great questions and I apologize for missing them on the chat. You hit the nail on the head that I was inundated during the chat. My typing skills are definitely not what they need to be!

    I have to throw out my disclaimer here. We (M-Vac guys) are not forensics experts by comparison to many that are out there. We are however, with a fairly high degree of certainty, experts in wet-vacuum collection, so keep that in mind. It’s amazing though how much we are forced to learn when introducing new technology like the M-Vac.

    I’m not sure there is a good answer to your questions though, or at least not a complete one. Certainly a hot area of discussion! From all the conversations we have had with forensics folks, the problem with mixtures, especially at the swabbing level, is that often times the amount of DNA material collected from the suspect, victim and anyone else who may have contributed DNA material at the point of deposit, is usually limited so there may not be enough “target DNA” to overcome the background noise during amplification. That is a primary reason that lab folks discourage processing samples that are from high traffic areas as the number of donors will likely be too many to produce a viable profile. I think in time this will be improved by increasing the number of alleles in the profile but for now we are restricted by what is available. Am I on track thus far?

    When working with an M-Vac sample the potential of this same scenario absolutely exists. However, the primary difference is the M-Vac will usually pull up more DNA material from the same location, assuming there is more there, which in our experience there almost always is. The question that we don’t fully know yet is what does that mean? In the “hoodie” case as we call it, the results from swabbing was a weak mixture, yet when the investigators re-sampled the same area with an M-Vac it collected a higher ratio of primary donor DNA material, providing a major DNA profile. That has happened in other cases as well but we don’t know yet exactly what the significance is, or if it is consistent across the many scenarios. What we do know is that in a number of cases the total DNA material collected has been significantly more than the swabbing method, and in most of those the ratio of major contributor to the minor has been better/higher, allowing the scientists who deciphered the data to make better conclusions. Obviously the M-Vac needs more casework experience and research data behind it to say conclusively exactly what is happening, but it definitely opens up a different mindset than what is generally accepted when swabbing or taping.

    One area that the M-Vac definitely opens up is the concept of the “archeological dig” and the chronological order of DNA deposits. The question of whether the last person to touch a substrate is actually the DNA material that is closest to the surface is one that I think is paramount to get answered. We are not exactly sure how yet but in time I know the scientific community we are working with will figure it out. Frankly, we are just very excited to be a part of it.

    Another question that comes into play with the capabilities the M-Vac brings to the equation is when a swab or tape sample comes up blank, does that mean there is no DNA there or does it mean that the method used just didn’t collect it? I’ve had numerous detectives, CSIs and lab folks alike think back to all the evidence they have seen and/or processed while pondering that question and it’s pretty amazing to think about. The “what-if” factors start coming in fast.

    Lastly, and I apologize for the lengthy response, is that we manufacture all of the M-Vac consumables and guarantee their sterility. We either gamma or EO sterilize everything, and that is after production in either a white room or a clean-room. The Nalgene filters that we recommend after the sampling are produced by Thermo Fisher so we are confident they are sterile as well.

    I imagine this has produced more questions than answers! Please let me know what else I can do to confuse the subject!



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  3. […] especially if the raincoat has been properly preserved. An examination of the raincoat with the M-Vac could tell us more about the person(s) who wore that raincoat by testing the armpits and the collar […]

  4. […] If somehow we still had that note I’d love for it to be scanned with the M-Vac! […]

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