well well chaps this could go on and on, and is the sort of question i love, espesialy having trained people to inspect trees, been an expert witness on more than one ocasion, and oftern asked to review reports through mediation and complaints procedures.
there has been some interesting stuff in the courst of late that looks at experts for tree inspecting and also cout work
poll v batholemuew here
http://www.aie.org.uk/resources/case_law/aie_case_poll_barth.html
this was interesting for many resons not least of all the ding ding that kicked off regarding servay methods after the case, but more because in the judment there was a genneral acceptance of a tearing to the type of inspection and the person doing it.
ergo if u r a forester do that not arb inspections, and visa versa.........
as goes experts in court this was a daming inditment of an expert who got it all a bit higgldy pigldy and shows the need to prepair the judge was not happy it would apear
atkins v scott
http://www.aie.org.uk/resources/case_law/aie_case_atkins_scott.html
having said all of that it is important to go to the basic rule if you know what you are doing and are certain of your facts qualifications are not always the only whay to show competence to do so, a good freind of mine stood with an NC arb in court against a chap who had PD Arb bs this cert that, the latter got some information wrong and bang.... he lost for that side.
but lets remember what are quals about, well showing you have knowlge in a certain area, and the courts love them, your customer feel happyer with them, and you will help become all you can by gaining them, but never be temted to go out side your area of knowleg, forinstance it has been about 7 years since i did any real subsidance work, and befor that it did not form the main area of my work, so i would be very carful befor getting too involved with a case of that sort, but give me accident investigation dangerouse trees, im your man.....
on a final note in case you have not seen it the hse do give some guidance in a SIM to the LA EHO's as to how to look at the risk assessment side of tree hazard inspection
have a look hear
http://www.hse.gov.uk/foi/internalops/sectors/ag_food/1_07_05.pdf
cheers all
kev