For any witness who saw something of significance, the sight angle should be checked. Where exactly was this witness at the time? What (or who) could he/she have seen? Was anything or anyone in the way?
Photographs should be taken of these angles as routine - and the position of the camera marked on a map which you draw the scene of crime. There may be a map drawn by the police in the evidence at trial; you can use a copy of this, but always beware - in case certain angles on the police map have been changed for one reason or another.
Video of the scene is useful - but appeal court judges are not likely to watch it, they consider it to be inadmissible ( don't bother asking why it' s just one of the rules of the game). The first case where the defence used video was at the trial of a murder near Hull. In that case the police had taken a video of the scene to demonstrate that the accused could have seen the victim from where he had been at various times during the relative period. However, they did not a) take note of which camera and what lens were being used; they shot it in August when the crime had taken place in March - and they shot in mid day when the crime had taken place in the evening .They later decided they did not need this video (we wonder why) - but the defence got wind of it and demanded it. One thing it showed was that a line of bushes - without leaves in the video, would have obscured the victim from the suspect if they had had the leaves on them as they had in March. Further, the darkness of a March evening would have obscured the victim even more in those circumstances.
In a case in Bradford, the convict was supposed to have seen the victim from his house across some rough ground. Simply looking at a map seemed to confirm that this was possible. But some houses were being built nearby at the time - and a large mound of earth had been built up between the two locations. Flying a balloon demonstrated that the suspect would have had to be standing on the roof of his house to see the victim where she had been. A further unfortunate aspect was that the police presented a map at the trial which was actually out of date - it seemed to place the victim closer to the convict's house than in fact it was.
Depending on the passage of time since the crime and your inspection, you should check out all possible changes - such the erection of fences and the cutting down of trees.
If the crime took place inside a building, you must be very careful. Many people are more sensitive than you may imagine If they have had a good financial deal on the house they live in, getting it very cheap, they will not wish to know that a gruesome murder took place in the master bedroom - and that there was a large pool of blood on the floor. Bear in mind that these people may be key to your investigation later on, so approach them with extreme care, and do not tell them any gruesome facts until you are sure they will cooperate with you.