morenohijazo Wrote:Y muy bueno, Holl. Buscar lógica en los peones. Muy bueno.

Antonio Iglesias Wrote:Es una de esas cosas a las que no le das importancia hasta que dejas de jugar contrarreloj y dices: 'Voy a repasar todas las gráficas que hay'. Me di cuenta viendo fotos de la pericial. La dinamita contiene almidón y ese almidón tiene una granulación que se puede teñir. Vi la enorme similitud entre la muestra que dicen que apareció debajo del asiento del acompañante de la Kangoo y la llamada muestra patrón. Pensé que estadísticamente es imposible o extremadamente improbable que dos cartuchos diferentes tengan la misma granulometría. Esta técnica analítica es habitual en la Policía Científica precisamente para discriminar tipos de explosivo en base a su granulometría.

nanu Wrote:Pero es que, además, en palabras del propio Iglesias:

Antonio Iglesias Wrote:Es una de esas cosas a las que no le das importancia hasta que dejas de jugar contrarreloj y dices: 'Voy a repasar todas las gráficas que hay'. Me di cuenta viendo fotos de la pericial. La dinamita contiene almidón y ese almidón tiene una granulación que se puede teñir. Vi la enorme similitud entre la muestra que dicen que apareció debajo del asiento del acompañante de la Kangoo y la llamada muestra patrón. Pensé que estadísticamente es imposible o extremadamente improbable que dos cartuchos diferentes tengan la misma granulometría. Esta técnica analítica es habitual en la Policía Científica precisamente para discriminar tipos de explosivo en base a su granulometría.

la granulometría es una técnica que utiliza la policía científica para discriminar diferentes tipos de explosivos, no diferencias entre el mismo tipo de explosivo (que es lo que pretende hacer el afamado químico)

pedrulis Wrote:¿No analiza los datos de ninguna forma?

Quote:Q. As a matter of fact, at your lab in the trace explosives
facilities, you can't just come walking in. The door is
locked; right?
A. Yes.
Q. And anybody that comes in, they have to follow a strict
procedure before they come into the trace facility; right?
A. Yes.
Q. They have to wash their hands?
A. Yes.
Q. They have to be swabbed to ensure that they're not
contaminated -- their hands, I mean.
A. Not visitors. Anybody that's actually working on case work
swabs their hands.
Q. Visitors wash their hands?
A. Yes.
Q. Put gloves on?
A. Yes.
Q. They wear those Tyvex suits -- is what they call them here.
I don't know what they --
A. Tyvex suit is better than a bunny suit.
Q. Okay, bunny suit.
Now, what about their feet?
A. They would wear, again, Tyvex overboots.
Q. Okay. Do you have one of those things like a sticky mat
that they step on before they come into the trace facility?
A. Yes, that's right, like a flypaper.
Q. And everybody has to walk across that?
A. Yes.

Quote:Q. Okay. How about quality control at your lab? Do you all
have a system whereby you make a general sweep, if you will, of
the explosives trace facility to determine for general
contamination from time to time?
A. Yes, we do.
Q. How often do you all do that?
A. Some areas are done on a weekly basis, and other areas less
frequently.
Q. And that's done so that you know -- you know what the
general contamination level is in the lab at any given time;
right?
A. The general background levels, yes.
Q. Because every lab is going to have a problem with that;
right?
A. It depends -- it depends on the lab and the type of work
they do.
Q. I didn't mean to call it a problem. Every lab is going to
have some general level of background contamination if they
work in trace analysis?
A. It depends on what trace they're looking for. But yes --
yes, I mean -- I wouldn't imagine all labs would have an
explosive --
Q. Correct.
A. -- trace backgrounds. It's just that's our area of work,
so that's what we've got to monitor for.
Q. Sure. Now, the reason that you do the quality control or
the general sweeps is so that you can keep the level -- keep it
at a certain level; right?
A. Not so much to keep it at a certain level. It's so we know
what's there.

Quote:Finally, the role of the EU with respect to the receipt of evidence should be modified to strengthen protections against contamination. Instrumental techniques have become very sensitive in detecting minute traces of explosives, which only magnifies the importance of preventing contamination of the evidence by persons handling it or from other materials present in the work area. Swab kits, clothing, and evidence to be examined for traces of explosives would preferably first be sent to a designated area that is physically separate from the main EU facility. The area designated for the receipt of evidence requiring residue analysis should have strictly controlled access and appropriate procedures to monitor and prevent possible contamination.

Quote:In response to a draft of this Report, the FBI advised that it concurs in each of the OIG's recommendations. The FBI noted that a new Evidence Control Policy was issued in November, 1996; that evidence handling and contamination avoidance is a high priority in the design of the new FBI Laboratory; that evidence control will be addressed in the core curriculum for new examiners and in the annual seminar to be attended by experienced examiners; and that greater collaboration between the EU and the CTU has taken place on the issue of contamination avoidance.

Quote:C. Contamination

The FBI has implemented the OIG recommendation to modify the procedures in the EU (now EOG) to strengthen protections against contamination in the receipt and handling of evidence. During our interviews, however, we noted some confusion concerning the periodic testing of the EOG area for contamination. The MDU unit chief thought the Chemistry Unit (CU) was testing the EOG area for contamination, but was unaware of any reports of the testing. The CU unit chief told us he was not testing the EOG area for contamination. We were assured by the Laboratory Director that this problem would be solved and that the EOG area would be tested periodically for contamination. We note that it is important for the MDU to take responsibility for the testing of its own area, whether the testing is performed by the MDU, the CU, or some other unit, and that the MDU should make sure that it receives reports of the testing.

In response to the preliminary draft of this follow-up report, the Laboratory Director informed us that, after our interviews the week of March 30, 1998, the FBI significantly strengthened its procedures to minimize the risk of contamination in the MDU. These new procedures include weekly testing of the MDU area for trace amounts of explosives

ElKoko Wrote:Sobre la granulometría, Antonio Iglesias aporta cuatro fotografías (al microscopio) en una resolución pésima de otras tantas muestras: la M-2 (Kangoo), la M-3 (TEDAX), una M-4 (mochila de Vallecas) y M-9-5 (AVE).

No sé cuál es el método habitual, entre los expertos en explosivos, para realizar comparaciones de explosivos a través de su granulometría, pero el Perito Valiente lo hace a ojo: marca con un círculo una parte de algunas fotografías (en los círculos del libro no se aprecia prácticamente nada) y suelta cuáles se parecen y cuáles no. No incluye datos de concentraciones ni de tamaños (no hay ningún tipo de medición), por lo que si él lo dice... va a Misa.

Isocrates Wrote:El Titadyne de cañaveras me parece cada vez más una muy probable fuente de la contaminación de NG. La verdad es que ahora empiezo a tener ganas de ver las grabaciones de la pericial para comprobar si nuestros peritos seguían los estrictos protocolos anti-contaminación que parecen necesarios. Ya sabemos que uno de los primordiales -medir el nivel de contaminación en el ambiente y supongo que algunos instrumentos- no se realizaba.

nanu Wrote:

pedrulis Wrote:¿No analiza los datos de ninguna forma?

No es un extracto del libro, es de la entrevista de El Mundo.
No se cómo analiza los datos en el libro, pero según parece (por lo que cuenta elkoko) utiliza el ojimetro de precisión para tal menester.

morenohijazo Wrote:el palmímetro de precisión