If I remember correctly, Guidance used to say that if the validity of EnCase as a tool is questioned, they will come to court and defend it. Not sure if it's still the case though.
Yep, but there are "several" layers of possible issues in a court or in a report.
The main stages are
1) retrieval of data
2) interpretation of data
3) analysis of events that may have led to the presence of those data and hypothesis on what has actually happened
A "good" software may be 100% correct in #1 and #2 but #3 pertains to the knowledge and experience of the forensic investigator more than anything else.
As well a "recognized" or "accepted" software (and a proper and properly documented procedure in it's use) may help in taking #1 and #2 as "granted" (and thus allow to focus the attention on #3 only, "jumping over" #1 and #2) but the "bigger" potential issues are still in #3, AFAICU.
Sometimes it is forgotten how a tool is only a tool and what may make a difference is more likely to be in the capabilities of the one that use it.
jaclaz