I have a broader issue (although it is linked).
Why is some evidence admissible in court and other evidence not?
A very broad answer is that some evidence is objective and repeatable, and is capable of being viewed in the same way by different people. e.g fingerprints, DNA results, a written statement, forensic matching of a bullet to a gun etc etc.
Other evidence is subjective, and depends on circumstances, interpretation. Dog alerts would come into this category - a dog is a tool to narrow down and aid the search for forensic evidence. and it is the results of such analysis which constitutes evidence.
Whether the dog alerted in down to Grime's interpretation of what constitutes an alert. That is why it would need to be corroborated by forensic analysis.
A question -would you be happy, say as a member of a jury, to send someone to prison for life on the basis of the video of Eddie searching the flat and the car?