| Author | Message | ||
     Steve |
Paper is a good source for developing fingerprints, which is mainly due to absorption of the residues on the ridges of the finger, and the difficulty in "wiping them off" that is found with porous surfaces where the print is on top of the surface. The procedure itself is not very costly. But, you also have to pay a person with the skills necessary to develop the print using the previously mentioned methods (salary, benefits, etc...), pay a person with the skills necessary to recognize a print of value that can be compared if there is someone for them to be compared to, pay a person to run the print through an Automated Fingerprint Identification System if there isn't a subject for comparison, pay a person to do any subsequent comparisons to any candidates produced, pay a person to write reports for everything they did, pay a person to testify in court as an expert witness, etc... Often this is just one person, the Latent Print Examiner, that you have to pay to do all this. This is not always the case though. There is also the cost of training the person to consider too. And with all that being said, nothing guarantees that prints will be developed, that prints of comparison value will be developed, that prints of AFIS value for search will be developed, that the prints developed will either match a given subject or anyone in the current database, etc... Any prints developed could be matched to a person legitimately in contact with the item. At the same time, if there isn't a known suspect, assuming the person who actually committed this hypothetical crime belongs to the prints - they may have never been fingerprinted before and their prints would not be a part of any searched databases. So when it all comes down to it, there's a lot more to answering your last question than saying a simple "yes" or "no". One must also take into consideration the budgets of the department, whether or not they can afford to have their own lab. Many smaller agencies must send their evidence off to state labs, etc... So as this thread is progressing and growing, if I may ask, is there a specific situation you are referring to in the hypothetical? It is very tough to try and create a hypothetical that matches a specific situation exactly. | ||
| David Fairhurst |
In an Ideal World. Unfortunately this world is far from ideal. First of all we must deal with increasing workloads, decreasing resources and endless bureaucracy. Secondly, we can never be sure of developing latents on any item, even if it has definitely been touched. Finally, the quality of the latents cannot be guaranteed. This has a bearing on both the possibility of an identification being made and the time it takes to get it once the overworked examiner finally gets round to dealing with that case. Don't expect to have someone banged-to-rights within a couple of days of submitting a scrap of paper to your lab. It will rarely happen that fast. | ||
| soilworker |
So basically, paper or porus surfaces are great fingerprint recources as long as they are not subjected to water, heat, or any damaging chemicals right? It usually doesn't take that much time or money and a couple days in the lab and the criminal should be found. | ||
| David Fairhurst |
Ninhydrin and DFO are very simple and quick treatments although DFO requires a special light source. The cost of the chemicals is probably counted in cents-per-item. PD is slightly more lengthy, tricky and expensive. Routinely in our lab we perform the most appropriate single treatment for run-of-the-mill thefts, burglaries and autocrime. Where the severity of the crime requires (major fraud, violence, rape, murder, arson) we can use all 3 sequentially DFO -> NIN -> PD to maximise the possibility of recovering evidence. This is not uncommon practice and is in no way considered a disproportionate use of resources. | ||
| Steve |
We do procedures such as that (paper processing) on a daily basis for residential burglaries and attempted auto thefts, let alone felonies. If the evidence is submitted for prints by the officer or detective, the case gets worked. Non-porous processes aren't that time consuming unless there are a lot of prints developed that need to be photographed. DFO requires the use of an alternative light source to illuminate the developed latents. The ninhydrin development can take some time, but that's usually just sitting. Some departments will speed up the process by using a steam iron, or another device that increases the temperature and humidity. But the actual time spent working with the evidence isn't that long. As far as "minor felony" goes, most felonies get priority. Arson is usually a high priority, especially if there seem to be several that may be linked. | ||
| soilworker |
Now how much money and time would all that chemical processing take, and would the investigating officers go to that extent for somthing such as a minor felony like 2000-3000 arson or 2000-$3000 grand theft. Or do processes that involve that much research and time only concern to Homicide or a major felony. | ||
| David Fairhurst |
YES. As long as the sweat (or whatever the print is made of) can soak into the paper. The disolved salts and amino acids and the fatty constituents would then be left 'inside' the paper and no amount of rubbing would remove them unless it damages the paper. recovery of prints on paper is already very well researched. Amino acids react with a chemical called ninhydrin to give a pink/purple colour. There is also a chemical that will react with amino acids to give a product that fluoresces under ultra-violet light (just in case your prints are on dark coloured or patterned paper) this is called 1,8 diazafluoren-9-one or DFO for short. If the paper has been wetted since the fingerprint was left then these processes won't work because the amino-acids will be blotted through the paper. However a silver reduction process known as Physical Developer will deposit grey/black silver metal where the fatty deposits are and making the fingerprint visible. | ||
| soilworker |
Is it possible to still be able to get latent prints from a paper surface if it was first touched by bare fingers or hand and then a few hours later rubbed over with plastic material or cloth material like gloves, or a bag? And if so, what methods and how much research must be done to recover the prints? |
