Having access to the crime scene is necessary for investigating the crime. Questioning that is beyond stupid.
The Dutch Red Cross did not need to physically visit the Sobibor crime scene to investigate Sobibor when they interviewed all the survivors of the deportations to that camp from the Netherlands. They could be sent the results of the Polish investigation, which is what happened.
Nor did the French need to have access to Auschwitz in order to carry out their investigation when they interviewed French Auschwitz survivors.
They sent
their results to Poland, who carried out a separate investigation which included inspecting the site and conducting chemical tests, among other things.
When the West Germans came to investigate Treblinka, they were sent the results of the Polish investigation in 1945, including the crime scene reports and crime scene photos. They did not need to reinvestigate the site because there was nothing there that would help them prove or disprove the guilt of the suspects. They were dealing with an already proven fact that was simply not in dispute by any of the suspects, none of whom denied that Treblinka had been an extermination camp.
Likewise, when a West German state attorney's office was investigating Auschwitz, it too was sent the older results, and then brought the case to trial, at which point it was felt that to resolve issues arising from court testimonies, a visit to Auschwitz would be helpful. So they arranged a visit and walked the ground, which led to a number of eyewitnesses' testimonies being thrown out since they could not physically have seen what they claimed from the vantage points they had described. The same consideration wouldn't have applied to Treblinka, because the entire camp was dismantled, whereas the main camp at Auschwitz was still standing.
As the materials available to the West Germans included the 1946 Sehn report, then the West German investigators would have known that whatever they were presented with in the 1960s when they saw Krematorium I was a reconstruction. Whether or not that fact was stressed, noted or emphasised was however irrelevant to the purpose of the trip, which was to establish whether eyewitnesses had line of sight to events they had claimed.
In the 1970s, East German investigators were sent materials from a Soviet province showing the precise locations of graves of partisan suspects who had been executed by the Secret Field Police. These materials included the 1944 exhumation reports and photos taken at the time showing the condition of the ground and also showing where memorial markers were placed to commemorate entire villages that had been wiped off the map, along with maps showing where they had been.
Your apparent pseudolegal proceduralism is a dead end for the following reasons:
1) crime scenes are generally investigated
once. Very few crime scenes are revisited over and over again and dug up or retested. There is especially little reason to revisit crime scenes when no defendant or suspect is raising any issues which might actually be resolved by revisiting the crime scene or metaphorically "exhuming the corpse". None of the recent archaeological investigations were conducted in a legal context; archaeology is a separate endeavour to criminal investigation.
2) it is perfectly possible for investigations to yield concrete results about crimes without involving forensics. This happens all the time when different police forces cooperate with each other. A crime happens in one district and is investigated there, but ramifications emerge which require the involvement of a neighbouring police force, who are sent the results and then generate new leads by standard police investigative means - interviewing witnesses. Or someone is sent off to check records (documents) and this yields results.
3) the basic point of what I wrote in the previous post to which you replied is this. The Polish and Soviet investigations
were trusted on the crucial points from the 1940s onwards
because there were other investigations unfolding entirely independently of these two states which came to the same results by other routes. Thus legal investigators, commentators and historians could see that there was evidence from this country, that country and the other country, and it matched the picture being developed by the Polish state and the Soviet Union, but especially the Polish investigations when talking about the death camps.
Those investigations were clearly trusted, because the Holocaust became an accepted historical fact by the end of the 1940s, as a result of combining the evidence uncovered in the east with the evidence uncovered in the west.
Cold War suspicions meant that there was probably more distrust of the Soviets, who were also more secretive and did not do much to publicise their investigations. But this only reinforces the basic point about the independence of the investigations.
The Einsatzgruppen trial relied exclusively on documents; only 2 witnesses were presented by the prosecution and there were no forensic reports used. The Americans could have asked the Soviets for thousands of forensic reports which had been drawn up from 1943-45 as the sites were investigated, but they didn't, because the trial took place in the time frame between the Soviet rejection of the Marshall Plan and the start of the Berlin Blockade.
Today, we can easily compare the two halves of the torn-up card and find oodles of corroboration, convergence and game-of-snap matches between the US investigation and trial of the Einsatzgruppen leadership, and the Soviet Extraordinary Commission investigations. These two investigations took place entirely independently. That is the best guarantor possible that neither was fraudulent.
Quite clearly, the results of the Einsatzgruppen trial were enough to convince western historians as well as western legal investigators through the whole of the Cold War that the Nazis had carried out mass murder in the occupied Soviet territories. That is
what happened - people were convinced by the evidence in the west alone on this part, because they simply didn't know about the full extent of the Soviet investigations. It wasn't until well into the West German investigations of the 1960s that copies of the 1940s Soviet investigative reports were sent to West Germany. But once they were sent, then these confirmed what was already being developed from the documents and the witnesses. They were independent sources.
Far from casting any serious doubt on the historicity of the Holocaust, the east-west split negates the quibbling of Holocaust deniers because the investigation of the crimes proceeded independently on both sides of the Iron Curtain to the point where it is
impossible to claim a massive forgery/fabrication exercise.