CLPEX Chat Board

Has anyone found a good way to test fingerprint reagents? Just for hypothetical discussion, let’s use ninhydrin as an example. It seems to me that someone could either test the entire bottle of ninhydrin right after it’s made or test it prior to every use.

If we test the bottle of reagent then what guarantees that the reagent hasn’t degraded or been contaminated over time? It doesn’t seem like this type of testing gives the same reliability for the beginning of the bottle as it does for the end of the bottle.

If we test the reagent prior to each use, it seems like your doubling your work load by first processing a test item and then processing the evidence. This just doesn’t seem practical. In using this testing system, if you test the reagent and use it and then need to use it again later that day, do you test it again or is the original test adequate?

Years ago we didn’t test our reagents and we never had a problem but standards changed and we changed along with them. Now we test our reagents. The problem I have is that it seems like this type of testing doesn’t insure that our reagents are working, it just gives the perception that the reagents are working. If I’m going to have a process in place I’d like to feel like it’s really worth doing and not just being used to pacify others.

In reality our office uses a bottle of ninhydrin very quickly so the reliability of the testing the bottle is probably the same for the beginning of the bottle as it is the end of the bottle, but this might not be true in every office or for every reagent. The true test in my mind, is to see that there was a reaction when the ninhydrin mixed with any amino acids in the paper (the ruhemann's purple color). I usually process so much paper at one time that there’s always a reaction on one of the papers. If all of the papers showed no reaction then I might be concerned that the ninhydrin wasn’t working.

Anyway, my question is does anyone have a testing procedure for all reagents that they feel works well to test the reagent, works in an ASCLD/Lab Accreditation environment, and is efficient and sensible? I’m almost positive that I’ve read that ASCLD/Lab does require that reagents be tested.

Thanks,

From a previous discussion board:
www.clpex.com/board/threads/2003-Aug-07/498/513.htm



l-alanine is an amino acid available through chemical warehouses and is of a controlled concentration.

Quality Control of Ninyhdrin and other Amino acid reagents is as follows:

To ensure the quality, the following serial dilution can test the integrity of the formulation for reaction and sensitivity. Apply the l-alanine dilutions to a piece of paper and allow to dry. Process with ninhydrin or other amino acid reagent and view reactions.

A reaction should occur at the 0.001 concentration and up. If not, discard the reagent solution.

concentrations
(0.1) gm l-alanine in 100 ml of water
(0.01) gm l-alanine in 100 ml of water
(0.001) gm l-alanine in 100 ml of water
(0.0001) gm l-alanine in 100 ml of water

My working in an ASCLD certified lab is now dated by 3 years, however my recollection is that documented testing of latent print reagents by batch at time of creation was required (we kept a central log). Also, a documented shelf life was required, and each container of reagent had to be labeled by batch identifier and dated.

Testing of ninhydrin on first use (per batch) each day was done by each examiner; to insure continued viability of reagents, test samples would be included with cases run, and documented in case notes. My lab was fortunate to have individual workstations for each examiner. Although most reagents were mixed centrally, small amounts of reagents were typically kept at each individual workstation.

Variations in work environment would dictate protocol and method of ducumentation, as well as current ASCLD requirements..

I agree that at some point the testing becomes overkill, however daily testing only when a particular reagent is actually going to be used may be an acceptable compromise.
Regards, RLT

Our laboratory director interpreted ASCLD documents as requiring testing of reagents for each case examination. So, even though we test ninhydrin at the time we mix it, we test it again immediately in each case prior to processing evidence with it. For ninhydrin, that means I treat a test print and if it develops, then I immediately treat my evidence. If I do another case later in the day, I repeat the test before processing the evidence. Likewise, we put a test strip in the superglue cabinet every time we run the cabinet. Our notes must reflect that each reagent we use in a case was tested prior to or during its use in that case. During the original discussions prior to making it laboratory policy, the lab director proposed that we also test powder prior to each use, but he finally conceeded that powder is not a reagent in the sense that liquid solutions are and he let us off the hook on that one, so at least we can get our powder out and start using it without first testing it to make sure it still works.

I guess I’m having a hard time figuring out the difference between testing the reagent and testing the examiners ability to use the methods correctly and at the appropriate times.

As an example, by putting a test print in the CA tank are you testing the ability of the CA to work or are you testing if the examiner left the items in the CA tank long enough? CA will work if used appropriately and under the appropriate conditions (or is that too big of an assumption?).

Another example with CA, suppose your test print is very fresh or on the perfect substrate. CA may work more quickly than it would on actual evidence where the moisture in the latent prints may have evaporated. The test print may make someone stop the process prior to it working on the actual evidence.

If the point of testing a processing method is to insure it’s working at its optimal level then maybe testing magnetic powders may not be such a bad idea. Over time the mixture may settle or maybe the powder element may decrease, meaning that it’s not working at its optimal capacity. But how often should something like this be tested? Daily just seems ridiculous. It sort of seems like we’re testing this every time we use it.

I feel the same way about CA. When my evidence is in the chamber, I’m looking for a good reaction. If it happens, I accept it. If it doesn’t happen, I try it again. Due to other factors (substrates, humidity, temperature, etc) sometimes I need to continue the process until I see a reaction. If I continue processing with CA and don’t have a reaction then I wouldn’t only consider that maybe the chemical isn’t working but maybe the heating element or the humidity device may be failing. I feel like I’m testing all the possibilities each time I process a piece of evidence.

I understand that my sort of testing (testing the reagent by processing evidence) may seem inappropriate, some people may claim that better controls are needed. We can implement controls but these controls seem to me to be artificial safety nets that really don’t work. They create the illusion of having appropriate controls but they really only waste time.

Michele Triplett wrote:Has anyone found a good way to test fingerprint reagents? Just for hypothetical discussion, let’s use ninhydrin as an example. It seems to me that someone could either test the entire bottle of ninhydrin right after it’s made or test it prior to every use.

For Nin I think the serial dilutions spotted on test strips (and dried) are simple and effective.

Michele Triplett wrote:I usually process so much paper at one time that there’s always a reaction on one of the papers. If all of the papers showed no reaction then I might be concerned that the ninhydrin wasn’t working.

I understand your point about testing overkill but there is such a thing as insufficient quality assurance also. The trick is to strike a balance between zero testing and overkill testing that just wastes time, as you so aptly mentioned.

Michele Triplett wrote:Years ago we didn’t test our reagents and we never had a problem but standards changed and we changed along with them. Now we test our reagents. The problem I have is that it seems like this type of testing doesn’t insure that our reagents are working, it just gives the perception that the reagents are working.

My question is how did you know you were developing all the latents possible if you didn’t do a test to ensure the reagent is working properly? Your scenario of processing hundreds of documents and being satisfied if a single page reacted would not bolster my confidence. Because amino acid content is variable, you should get varying degrees of reaction throughout your evidence. Because of these variables we need a control. I would prefer that control to be a measured (known) amount of amino acid. I think that test is better than doing nothing, and is also better than soup, and saliva, and urine, and it should be simple enough to perform.

Oh and don’t forget to measure another important variable also: Your humidity level. If you are not using an environmental chamber I think you would do well to invest in one.

My 2 cents.

BR

Maybe ninhydrin was a poor example because I do recognize the need to test this reagent regularly, I was really asking a broader question about testing any and all reagents. I’m wondering if testing could be broken down into different categories according to different types, instead of having one overall policy to cover all processing methods. While testing some processes daily or per use seems justified, other processes may not warrant this kind of testing.

For instance,
a) test all processes at time of preparation in addition to:
b) test reagents per use that create a chemical reaction to produce visible ridge detail (ninhydrin, dfo, indanedione, 5-MTN)
c) test fluorescent dye stains weekly, biweekly, or monthly (I’m basing this on my belief that the degradation of these is in the fluorescent properties and this degrades slowly not all of a sudden)
d) test powder suspensions at time of preparation
e) test non-fluorescent dye stains at time of preparation (amido black, sudan black, gentian violet)

I haven’t fully thought this out or tried to put all our processes in the groups to see how many groups there’d have to be but there may only need to be 3 groups (a, b, and c, since d and e are covered in a).

Is anyone aware of agencies that test different methods differently according to what’s needed or is it just easier and less confusing to test everything the same way (either by batch like RL Tavernaro did or per use like Pat does)?

Dear Michele,

To simplify, I think it is important to first decide why you are going to perform the test.

If you are testing a batch directly after it has been prepared, you are ensuring that the starting materials were not faulty/contaminated. By doing this straight away, it is easier to identify which component was at fault if a problem arises, rather than coming back to it a few weeks later, by which time the faulty material could have been used to prepare other reagents and wasted a lot of your resources and time.

If you are testing just prior to use, you are ensuring that there has been no degradation of the reagent over time, and in addition you are demonstrating that you have obtained the maximum development from the evidence with that reagent, so there is no chance that there is a fingerprint left behind that could have been and was not developed by that particular reagent. (I hope this makes sense!)

With regard to regular testing of reagents in between, you have to decide between the following scenarios:

(1) At the time of the treatment of the evidence (for example at the crime scene), you have limited time for reagent preparation in the advent that your old stock is no longer performing optimally when you test it. In which case, it is better to test it regularly when you have the chance, so that you can detect defective reagents ahead of time and minimise the chance that you will turn up a "dud" at the time of evidence processing.

(2) You have time to prepare reagents at the time of processing the evidence in the advent that your old stock is not performing optimally. In which case, regular testing of the reagent is a redundant exercise.

With regards to individual reagents, it may be useful to use the reagent stability as a guide to how often you need to test it.

I hope my opinion helps,

Kind regards,
Shaheen Aumeer-Donovan

I think it is important to test the reagents and DOCUMENT that in your notes when you are processing the evidence. According to ASCLD/LAB, that needs to be in the case record.

The reagent needs to be tested when it is first made to ensure that is working and giving valid results. The reagent then should be tested prior to processing evidence to ensure that the reagent hasn't degraded and is still giving valid results. This needs to be done prior to the evidence processing and not during because if there is a problem you cannot go back. The evidence isn't in the condition that it was before it was processed. The question would come up, did the previous processing with the degraded or contaminated reagent now prevent the development of ridge detail when re-processed with a valid reagent. Probably it didn't, but you wouldn't know for sure.

Does the reagent need to be tested for each individual case? Good question....I think it does. In my office I try to batch process evidence from multiple cases so I only have to test the reagent once. But if I processed evidence in the morning using DFO, then another case came in late afternoon, I should re-test the reagent. Do I know its going to work, of course I do....but I need to be able to document in my notes that I tested it.

It does seem like overkill and like a waste of time, but how much time are we talking about really? Besides Physical Developer which is more labor intensive, most reagents this would take maybe 5-10 minutes at most.

Where I have problems is testing things that don't really need to be tested. For example, R6G, Ardrox or most other fluorescent reagents fluoresce because that is their physical property. I mix it up and by simply looking at the bottle I can see it is fluorescent, I can see that it is giving me a valid result. In my mind that passes the test.

When our office uses test strips in our CA chamber, it is to gauge when the reaction is complete not to show that the CA is working.

Just my nickel's worth.......

I think all breathalysers should be tested each time they are used; this would require someone to be with the officer at the time of the turn-over who has become drunk under controlled conditions, any volunteers?


Sorry, I couldn't help myself.

I'll drink to that!

I think Shaheen may have a good idea with stability. It would take a little resource in writing your SOP's, but with the physical techniques=no testing. With those where the stability is a year or more a test when they are made and every 3 months after that. With those that have short stability then a test when prepared and before use. Might seem a little complicated but it could make personnel realize more fully the shelf life of different reagents.

I never could really understand the Super Glue one since it is not really a reagent, but testing each time you use the tank is here to stay.

As someone said my 2cents.

Charles, I think that the reason a control is used to test the CA is not really to see if it working or not, but to gauge when you are likely to start getting over-development with the glue.

An older print will take longer to develop with CA than a fresh print, so having a fresh control will tell you when to start being aware of over-development, particularly if you have a white or non-contrasting support that is difficult to see from the front of the chamber.

In the same way, older glue will also take longer to develop a print than fresh glue, so again you are looking at when over-development might start to occur without having to take the exhibit in and out to examine it.

I agree though, if you are not using the control in this way, it seems very pointless!

- Shaheen

Shaheen, I agree as I have always looked at the evidence as development is not the same across the board, especially when one is processing multiple cases in the fuming chamber at the same time.

But what I have seen being practiced lately is that the CST's are watching that strip and when that recent print on that strip develops they stop the process, remove their items and go on to the next sequence.

I think they miss some things as they are relying on the strip and not what they observe on the evidence.

But that is what they are led to believe. They are pounded pretty hard about over processing and it is natural for them to accept the position of "when the strip is done then then evidence is done".

I think that in the case of CAE Fuming the test strip can be "not too good of a thing". The interpretation and implementation of standards making a left turn instead of a right one.

Some would say that is a training issue and they may be right. However it sometimes takes years for someone to develop that knowledge, and experience to figure out what exactly is going on and how to use that information to make it work for them.

I do like your idea and I will try to see what I might be able to accomplish with it. Changing well established SOP's is kinda like licking honey off of a razor. If done right it is sweet, but if wrong, it is going to hurt.

In the CA cabinet we also use a test strip to confirm that the CA "worked." But we gauge the prints on the evidence by their own development. The test strip is advantageous when, after a suitable period of fuming with absolutely no latents visible on the evidence, you can see the test print nicely developed or even overdeveloped and be reassured that the fuming worked but the evidence was simply "clean." But for my two cents' worth, the main reason for the test strip in the fuming cabinet is because department policy requires it.