# Can the police detect illegals by X-raying the truck they are hiding in? **URL:** \ **Category:** Factual Questions\ **Created:** [November 29, 2003, 8:54pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960 "2003-11-29T20:54:47Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![pluralgravity](https://avatars.discourse-cdn.com/v4/letter/p/2bfe46/32.png) [@pluralgravity](https://boards.straightdope.com/u/pluralgravity)\ **Post date:** [November 29, 2003, 8:54pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/1 "2003-11-29T20:54:47Z")
We’ve seen a news item on the Beeb about this wonderful British invention, like a huge airport metal detector archway, which can X-ray a truck. They are supposed to scan trucks disembarking from cross-channel ferries and produce an image on which hidden illegal immigrants can be easily seen. I think this is a lie broadcast to discourage would-be illegals, but I cant prove that to my satisfaction. I don’t believe it for two reasons, firstly, this is Tony’s Britain and, hey, almost everything the govenment says is a lie. Secondly, the X-ray source would have to be so intense to penetrate even a curtain sided truck, never mind an alumium or steel cotainers, that any stowaways would get a dangerously large dose of X-rays. Bearing in mind that when these chaps are led blinking from their hiding places, they are presented with the finest legal aid that the British taxpayer can afford they are, to put it mildly, gonna sue someones arse off. ---
**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\ **Post date:** [November 29, 2003, 9:18pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/2 "2003-11-29T21:18:03Z")
If you can, check out the photo on pages 14 & 15 of the November '03 _National Geographic_. It’s an x-ray of a truck full of bananas with a few people stuck in amongst 'em. I didn’t find the photo online, but you can go read _National Geographic_’s [Watching You](http://magma.nationalgeographic.com/ngm/0311/feature1/index.html) article. ---
**Author:** ![bleach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bleach/32/3106_2.png) [@bleach](https://boards.straightdope.com/u/bleach)\ **Post date:** [November 30, 2003, 2:57am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/3 "2003-11-30T02:57:37Z")
I’m not sure if this is similar to the National Geographic image **Ringo** , but there is a thumbnail [here, on the AS&E site](http://www.as-e.com/technology/image_1.html) (image ASE\_03B). ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [November 30, 2003, 3:09am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/4 "2003-11-30T03:09:33Z")
Can’t be. Even if you were going to shoot such massive doses of x-rays through a truck, what are you going to use to pick up the image? You’d either need a giant film cassette to put on the other side of the truck (which would then need to be developed), or have one huge portable digital sensor. No way! ---
**Author:** ![robo99](https://avatars.discourse-cdn.com/v4/letter/r/a8b319/32.png) [@robo99](https://boards.straightdope.com/u/robo99)\ **Post date:** [November 30, 2003, 3:54am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/5 "2003-11-30T03:54:20Z")
I saw that photo in the National Geographic magazine too. Did they actually use X-Rays or was it infrared? ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [November 30, 2003, 5:21am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/6 "2003-11-30T05:21:08Z")
On the AS&E home page there’s a photo of the unit used to scan sea containers. Looks like the truck has a sensor on an arm that’s positioned opposite the source. As the truck passes down one side of the container, the detector is passong down the other side. I believe with the backscatter units the source and detector are colocated. ---
**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\ **Post date:** [November 30, 2003, 5:23am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/7 "2003-11-30T05:23:30Z")
> [@](#): > > \*Originally posted by x-ray vision \* > \*\*Can’t be… No way! \*\* Apparently, [way](http://www.as-e.com/technology/technology.html) > [@](#): > > Z® Backscatter is a patented, proprietary AS&E technology that is uniquely able to detect low-density organic materials in complex, high-density backgrounds. Z Backscatter X-rays do not need to penetrate through the dense materials in order to detect any low-Z (organic) materials shielded behind them. Instead, Backscatter X-rays reflect away (“scatter back”) from the low-Z organics without even encountering most of the high-Z (inorganic) clutter. Backscatter reflections define the organic signals as separate and distinct images. ---
**Author:** ![Ficer67](https://avatars.discourse-cdn.com/v4/letter/f/c57346/32.png) [@Ficer67](https://boards.straightdope.com/u/Ficer67)\ **Post date:** [November 30, 2003, 7:23am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/8 "2003-11-30T07:23:51Z")
Does it have to use x-rays? I mean some of the images could be thermal imaging images. Also there is equipment sensitive enough to detect human odors, bio-electric patterns, and the sounds coming from their beating hearts. So if customs agencies of the U.S. or Britain so desire, they can muster the technology to scan every cargo truck or container they wanted to without using x-rays, or putting the illegals in any danger what-so-ever. ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [November 30, 2003, 8:24am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/9 "2003-11-30T08:24:38Z")
The X-ray output required to create a gross, vague outline with the most sensitive electronic detectors is not nearly as high as the amount needed to create a detailed chest film that visualizes (among other things) sub-millimeter details inside the thick vertebral bones. Compare the light required by standard film or the human eye, with the amount required by a night vision scope. The night vision scope’s image is a far poorer quality, but it’s adequate for the task. A stoaway detector is more akin to a night vision scope than a vacation snapshot. 15 years ago, we had hand-held fluoroscopes that could display real-time images of limbs, joints and torso using nothing but a tiny fairly safe speck of isotope (Yes, safe- after all, the physician held the unit in his hand!) Total patient exposure was well under 1/100th (1/1000th?) of a chest x-ray. They were mostly used in orthopedics because they didn’t provide the detail and time-stopping snapshot needed of a chest x-ray full of subtle structures with a beating heart in the middle. Small safe sources of radioactivity are common. There’s a speck or Americium 241 in most smoke detectors, and many watch dials still use radioluminescence. For that matter, point a Geiger counter at a classic cinder block sometime. Ash is enriched in the heavier elements present in the original wood, including radioactive ones. > [@](#): > > I mean some of the images could be thermal imaging images. Also there is equipment sensitive enough to detect human odors, bio-electric patterns, and the sounds coming from their beating hearts. So if customs agencies of the U.S. or Britain so desire, they can muster the technology to scan every cargo truck or container they wanted to without using x-rays, or putting the illegals in any danger what-so-ever. Actually, this is pure science fiction. IR is a low wavelength photon, and is less penetrating and more easily diffused than visible light, as we all know from our daily experience with radiant heat. Thermographs of houses, taken to detect heat loss can’t see through walls; neither can the more detailed IR photos of our best IR nightscopes. In fact, even layers of warm or cold air can diffuse IR images. You might be misled by the "see-through clothing’ IR photos taken by some video cameras, etc. – but they only ‘see through’ flimsy open weave summer cloth. If you look at those same photos, you’ll find that anything more substantial still appears completely solid. There is no IR transparency. Human odors can be detected, if you’re willing to go inside each truck and sniff around - “electronic noses” don’t yet outperform sniffer dogs. Biolelectric signals can’t be usefully discriminated at any distance, outside of Star Trek. I’ve used them in many research projects, and even contact electrodes on the skin often need significant fiddling to get a good signal. The sound of beating hearts? Through a truck? Again, that’s a Star Trek notion. The number and volume of ambient noises would make discriminating the indistinct muffled throb of an heart (a sound I know well, as a physician) impossible in the the environment of an active checkpoint. Even in a quiet lab, with no other sounds, detecting a heartbeat from within a wooden box at a distance of 10-20 feet would be a very difficult challenge. People often think that mere amplification can solve many problems, but even when I was a child, it was easy to build an op amp circuit to amplify faint sounds by a factor of up to a million. Try it - you’ll soon learn how little use raw amplification is. Again, our daily experience tells us that sound is not a very localizable or penetrating form of energy transmission I’m not saying that someone might not someday develop a sophisticated computer to discriminate such delicate details. I’m simply saying that these are not particularly promising modes of detection due to their physical bases. X-rays are so much more penetrating and clear that we’ll probably have the ability to scan with ambient x-rays (the normal x-rays in the environment) or extremely low level sources with distinctive (hence easily distinguished) time or energy profiles. Why not? Cinder block, smoke detectors and watchdials use low level radioactivity ---
**Author:** ![Rayne\_Man](https://avatars.discourse-cdn.com/v4/letter/r/df705f/32.png) [@Rayne\_Man](https://boards.straightdope.com/u/Rayne_Man)\ **Post date:** [November 30, 2003, 8:38am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/10 "2003-11-30T08:38:52Z")
What British immigration officers are using on trucks are CO2 detectors. These can pick up the expelled breath from people hiding in trucks. This looks like a simple wand device which is quickly passed across the trailer of the truck. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 30, 2003, 8:58am UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/11 "2003-11-30T08:58:00Z")
> [@](#): > > \*Originally posted by pluralgravity \* > **Secondly, the X-ray source would have to be so intense to penetrate even a curtain sided truck, never mind an alumium or steel cotainers** It doesn’t have to be intense, it just has to be high-energy (i.e. short wavelength) radiation. Apparently AS&E’s backscatter imagers use 225 keV X-rays (according to [this PDF file](http://www.valleyassociates.com/XraySystems.pdf)) which will penetrate a 1" thick steel plate with only 30% attenuation. Lead and other heavy elements can be a problem though - a 1/8" lead plate blocks 90% of the radiation. Still, it would be recognized as a lead shield and arouse suspiscion. ---
**Author:** ![pluralgravity](https://avatars.discourse-cdn.com/v4/letter/p/2bfe46/32.png) [@pluralgravity](https://boards.straightdope.com/u/pluralgravity)\ **Post date:** [November 30, 2003, 2:40pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/12 "2003-11-30T14:40:52Z")
Thank you all very much for pushing back the frontier of my ignorance a little. I believe now that I was mistaken when I imagined that it would take a nad frying dose of X-rays to scan a container well enough to detect a stowaway. So the machine exists and would probably work. However, if someone were detected by this machine his lawyer is sure to claim that his client was exposed to harmful radiation without warning or permission and that only a large cash compensation award would restore his human rights. The machine is kept in a shed at Dover. It can be brought out for photo- oppertunities like ministerial visits, a boffin will press a button and the machine will go ‘PING’. Dogs and CO2 detectors do the job, but dont look nearly so ‘‘modern’’. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [November 30, 2003, 4:57pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/13 "2003-11-30T16:57:10Z")
> [@](#): > > \*Originally posted by pluralgravity \* > **However, if someone were detected by this machine his lawyer is sure to claim that his client was exposed to harmful radiation without warning or permission** IANAL but this seems a little farfetched to me. I don’t remember getting any warnings or singing any waivers when getting a medical X-ray. Is there really a case where an X-ray scan was declared as an unauthorized and harmful search? ---
**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\ **Post date:** [November 30, 2003, 6:21pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/14 "2003-11-30T18:21:42Z")
A fellow named Danny Kyllo was arrested in Oregon in 1992 after police used a thermal imaging device to discern heat attributed to lights being used to grow marijuana in his house. The Supremes ruled it an illegal search. From a [BBC story](http://news.bbc.co.uk/2/hi/americas/1384174.stm) > [@](#): > > In a 5-4 decision, the court ruled that police violated the rights of a man from Oregon in the Pacific North West by using a heat-seeking device without a warrant to determine if he was using high-intensity lamps to grow marijuana indoors. So, they couldn’t make that bust stick, but they have the means to learn a bit about your thermal signature. ---
**Author:** ![patchbunny](https://avatars.discourse-cdn.com/v4/letter/p/dc4da7/32.png) [@patchbunny](https://boards.straightdope.com/u/patchbunny)\ **Post date:** [November 30, 2003, 6:49pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/15 "2003-11-30T18:49:38Z")
> [@](#): > > \*Originally posted by Ringo \* > \*\*A fellow named Danny Kyllo was arrested in Oregon in 1992 after police used a thermal imaging device to discern heat attributed to lights being used to grow marijuana in his house. The Supremes ruled it an illegal search. > > From a [BBC story](http://news.bbc.co.uk/2/hi/americas/1384174.stm) > > So, they couldn’t make that bust stick, but they have the means to learn a bit about your thermal signature. \*\* I remember that case going through the courts. IThey couldn’t identify the grow lights per se, but the logic was rather part of his house was hotter than the rest, therefore: hot = grow lights = illegal activity. _Charge!!!_ Quite happy when the Supreme Court ruled it illegal. –Patch ---
**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\ **Post date:** [November 30, 2003, 7:34pm UTC](https://boards.straightdope.com/t/can-the-police-detect-illegals-by-x-raying-the-truck-they-are-hiding-in/215960/16 "2003-11-30T19:34:33Z")
I have to wonder if he pronounces his last name as “kilo.”