Public Safety committee  If there is a material that is an interferent with a particular narcotic, then there's really no way of modifying the machine to not react to it. When you're looking at the little graphs that the machine produces, if the wipes appear at the same place as cocaine, then there's always going to be that problem.

Public Safety committee  It could be a false positive in that case. We would not use that as an indication that somebody is positively carrying drugs.

Public Safety committee  The ion scanner is used as what we call a presumptive test, so if it looks like cocaine, it would lead to an enforcement action where the drugs are seized. Then typically, that sample will be sent to the Health Canada laboratory for verification that it is indeed cocaine. We don't rely on the ion scan uniquely, Mr.

Public Safety committee  I can't speak for my colleagues at CSC, but we certainly set the sensitivity.... Part of that is based on the number of nuisance alarms. We'll set it so it's not so sensitive that we're getting lots of nuisance alarms, but it's not insensitive.

Public Safety committee  Any of the identified interferent substances could, in principle, be used to mask a narcotic, or dirt. If you put a lot of dirt into a machine, it doesn't operate very well. As I mentioned, these are incredibly sensitive machines. They're looking for traces. If you have a bunch of junk in there, then it's going to render them less effective.

Public Safety committee  You raise a couple of good examples. What I would say is that neither of those are trace detection technologies. The muon technology is really for bulk detection. Neutron technology is also for bulk detection of material. You might find a brick of cocaine, but you would not find a trace of cocaine.

Public Safety committee  Whenever we're buying new equipment or replacing trace detection units, we put out a request for proposals. We include the technical specifications of how they're supposed to operate and what their performance is expected to be. They are posted freely. Anybody can bid on them. There are several manufacturers that make equipment like this.

Public Safety committee  The instrument does respond more strongly to an increased volume. However, we don't use that in our machines. It's either yes or no, above a certain threshold. We're looking for such tiny quantities, that if you have a nanogram here or two nanograms over there, it's still a very small amount.

Public Safety committee  There are false positives, as I described earlier, where there's no drug there, but it does give an indicator of a drug. We collect information on false positives over the years, and we think we have a fairly good understanding of which products can provide false positives.

Public Safety committee  Let's talk about false positives and nuisance alarms. A false positive is where you swab something and there's no drug there, there's no heroin there, but you do detect heroin. That is because there's an interference—

Public Safety committee  I understand. The nuisance alarms, which we're familiar with, are where you do detect very small amounts of drugs, and they're actually there, but the person is not carrying a significant quantity. We recognize this problem. For example, we don't swab currency, because the drug trade is largely a cash business.

Public Safety committee  I could take that question. That's exactly right, in that if we detect traces of a narcotic on the exterior of a bag, that gives us the motivation and the justification to go further. These scanners are incredibly sensitive. They're detecting nanograms of material. Nanograms doesn't mean very much to most people, but if you take a grain of salt, that's a milligram.

Public Safety committee  Sure. I would be happy to do that, Mr. Chair. In fact, I think there's a fairly good description from your previous witness in November, Professor Hannem. She went through that in some detail. How it works is that you use a piece of material to swab a surface and hopefully pick up traces of, let's say, cocaine.

Public Safety committee  That's absolutely how it works. We're quite careful about looking at different drugs and making sure they're well separated. We look for potential interferences. This doesn't actually look at every atom in the molecule and say exactly what it is, but each drug has a characteristic time in the machine.

Public Safety committee  Well, it's thought that the machines have become more reliable. They have had a lot of upgrades and better software, etc., but the fundamental principle remains largely the same.