The only dna possibilities from secondary "evidence" are...
1/Predator saliva swabbed from predated animals.
2/Scats.
3/Hair.
1/Saliva from kills-Assuming the kill is deemed to be odd, or associated with a crytpid for some reason, this is the lowest probablity of returning a species id due to saliva from predator, found on the prey animal being contaminated/destroyed by sunlight/heat/rain etc..
2/Scats-Some of the intestinal lining cells of the predator are stripped off during the movement through the body..and will be on the scat on the outside ....these would be giving you a chance to possibly id the predator species rather than the prey species itself.
Problems-Contamination from prey species dna/obvious contamination due to faeces itself/sunlight/moisture/heat etc.
Low levels of predator species dna and possible plant products(polysaccharides) which can inhibit PCR technique used to amplify dna, make scats quite difficult to work with.
3/hair follicles-Our best bet.!
Supposedly really needs the bulb at the base of the hair to be intact for a decent attempt at extraction/species ID.Some labs require 5 bulbs..I have read somewhere that some labs can extract MT dna from hair shafts...but other labs have suggested problems with extraction from the shaft iteself and prefer the bulb.
Grooming Hair can sometimes be found in scats.The problem again would be to separate predator/prey hairs..which unless they were visually different would require you to dna extract on all of them.
Often we will hear people say words to the effect of " well show us th dna evidence for....(insert cryptid )"
It appears to be associated with their own ignorance of how it all works.. but they have watched CSI or some other tv show and think its a snap..
1/Who has to pay for this..(we do)?
2/What labs are you supposed to use.?
3/Problems of sending samples overseas with time/xray machine etc.
4/Problems of finding labs in Australia(there are few and far between that will do this for "us")
5/The killer point-If the sample comes back with a high species id probablity(that is profound), then people will just turn round and go"you have just swapped the sample..or there is a contamination problem".
If you collect a sample of scat or hair for instance, and you think it can be used for dna/species id..oneday..the latest advice is to store the sample in a paper bag in a cool dry place.
Placing samples in sealed plastic bags leads to the the samples releasing/absorbing moisture and encouraging fungus/bacteria and hence rapid destruction of useable dna.
Another minor point-We have had NSW govt departments contact us, for advise on labs/methods etc ..since we are not scientists, and they have scientists of their own...we find this is very odd indeed..
And we had someone here awhile ago suggesting the hair from scats he had collected here had been sent overseas and he had been given a "result" as possibly ape like etc....ie, the inference was..the result was not known to science.
Visual examination(guessing) of hair for species id, is ...worthless in many cases.
We have blind tested several scientists who specialise in visual examination of hair/scats for species id over the years, all failed....
Back to DNA though...The paradox of the most cutting method in science today for species id, for us, is also....riddled with problems and costs..maybe in a few more years will have a field testing unit that can species id in minutes..
Apologises for the length of this rant..