Brain fingerprinting using EM field

I wasn't

I wasn't aware that lie detectors were out, and brain fingerprinting was in...

Apparently when they present a subject with a sensory target, they can get a very accurate response as to whether the subject recognizes the sensory target, or not. Basically they can read some responses of your brain directly. So if the operators of the equipment provide you with a target (a murder weapon, a photo of a person or a crime scene, a stolen item, some words etc.) they can tell directly from the electromagnetic field given off by your brain whether you recognize the target. http://brainwavescience.com/testimonial/

Judging from this Wikipedia article, there's a lot of scepticism about these claims:
https://en.wikipedia.org/wiki/Brain_fingerprinting

Looking into it a bit further, it seems there are two factions working on this. The criticism in the Wikipedia article was directed at Larry Farwell, who describes himself as the inventor of Brain Fingerprinting. The Brainwave Science company is run by another group, whose technology Farwell describes as "counterfeit":
"The technology that Ika, Kota, and Brainwave Science have been attempting (albeit unsuccessfully) to sell to governments is indeed “incredibly dubious.” ... the technology that Ika, Kota, and Brainwave Science have been attempting to market is a counterfeit technology  that  does  not  meet  the  peer-reviewed, published Brain Fingerprinting Scientific Standards. ... The dubious counterfeit technology that Ika and Kota are attempting to sell is untested and unproven."
http://www.larryfarwell.com/pdf/Dr_Larry...g_1604.pdf

Which seems to be pretty much what other people are saying about Farwell's technology.

It seems the objection is not so much to the principle of the technique, as to exaggerated claims of its accuracy.

The theory behind this highly dubious (as regards accuracy) piece of equipment is that brainwaves will change in a consistent and predictable manner based on being fed certain visual stimuli. So a suspect sits in front of a screen and looks at pictures of a murder weapon or a description of how the victim was killed etc.

The brainwaves are then monitored to detect "changes" (not sure what constitutes a change) during the process and if a certain change is observed, bingo, that must mean that the stimuli were already present in his/her brain and therefore the subject must be guilty. Used in the case below (from the inventors web site) it seems to have done the trick...however... we don't know that the only reason Grinder confessed is because of Farwell's gadget. Grinder (as well as being a piece of garbage) might have been a dimwit who believed everything he was told about the machine and therefore felt he had no alternative but to own up.

Grinder’s brainwave responses to the words and phrases containing details of the rape and murder of Julie Helton clearly contained a P300-MERMER, indicating “information present” which means that the details of this crime were stored in his brain. (As expected, the target responses also elicited a P300-MERMER, and the irrelevant responses did not elicit a P300-MERMER.)   
The Brain Fingerprinting system mathematically analyzes the brain-wave responses and makes a determination of “information present’ or “information absent”. “Information present” means that the probe responses, like the target responses, contain a P300-MERMER indicating that the crime-relevant information is stored in the brain. “Information absent” means that the details of the crime are not stored in the brain. The Brain Fingerprinting system also computes a statistical confidence for the determination of “information present” or “information absent.”
 
The Brain Fingerprinting test result for J.B. Grinder was “information present,” with a statistical confidence of 99.9%. From this we can conclude with a high degree of confidence that, even though fifteen years had passed since the event, significant details of Julie Helton’s rape and murder are stored in J.B. Grinder’s brain. 
[font=Times New
Roman]One week after Dr. Farwell's Brain Fingerprinting test on [font=Times New
Roman]him, Grin[/font]der, faced with certain conviction and probable death sentence, pled guilty to the rape and murder of Julie Helton in a plea bargain in exchange for a sentence of life in prison without parole.   He is now serving that sentence.  He also confessed to the murders of three other young women.[/font]

I can see loads of problems with using changes in brainwaves to make an accurate and consistent judgement. What about people with [b]a guilt complex? How do you factor that in. What about people with acute anxiety of being falsely convicted? Their brainwaves are going to go haywire when shown a weapon that they are suspected of using. Hell, some poor buggers can even be made to believe they are guilty even when they are completely innocent. I can't see how this gadget is[/b]
[b]even as effective as a polygraph, never mind superior.  [/b]

[b]Apologies for the (b)s can't remove them     [/b]