Face Value would mean that you accept the statements as the truth from that persons perspective, unless of course you have other information that they are deliberately lying or otherwise trying to skew the investigation.
The problem with all witness statements is that different people  interpret the same things in different ways. For example if you  look at the statements from a simple thing like a traffic light collission ( an every day occurrence)  and you will see quite different versions of the same event. some people will remember  very little , others will use their imagination to fill in the gaps. This is why witness evidence may be so open to questions. Some things you could be quite sure of for example if you were for example in the above traffic acccident you would know what car you were driving, but other things may happen so fast you dont really know what happened.
So imagine if  you saw something truly weird, suddenly and unexpectedly this could give any individual enormous problems explaining what they saw. Now add in the age gap of time, the fact the some people may be making money out of the event, the fact that we as a forumn  may be subject to attempts of  disinformation then there is a big problem with witness statements/ evidence.  Also witnesses making statements about the event are under no obligation to tell the truth---- they will not face conspiracy to pervert the course of justice charges or perjury.#
The way ahead is too accept statement at face value but try and obtain independent  corroboration of their content and even when this does not fit bear in mind the witness may be 1) telling the truth 2) was confused 3) lying 
Nice little problem eh? 
