Normally when we consider the matter of criminal investigation, we recommend a prompt investigation of the crime scene and interrogation of witnesses/collection of possibly relevant evidence. We should remember that conspiracy to commit murder is itself a serious crime, and that once a few such instances pile up, the sum of the sentences would be about the same.
Sometimes individuals obstruct a prompt investigation of a crime scene, or delay its report for hours. Oftentimes the scene has been cleaned up or altered. You might not even be able to tell whose handiwork is which after inspection, whether for a murder or for the cleanup. To use such ambiguity as the basis for reduction of sentences enables an alternative means to avoid murder sentences. Hence, if the involvement of the individuals in the affair is known (not the same as covering up a crime or obstructing justice without a known crime committed or proven to be linked to suspects), the correct approach is to treat all individuals as involved in all aspects of the crime.
Such considerations do not only extend to the physical crime scene itself. Individuals who wish to see crimes punished will ask for due process (e.g. paying for legal representation), but also will demand and facilitate (with proper documentation/warrant) the prompt, complete investigation that is required to enforce the law without resorting to vigilantism. Those who prevent this, by providing aid and comfort to notorious fugitives (whose presence cannot be denied), and obstructing access to evidence, may not be guilty of the crime, but have declared their open opposition to the enforcement of the law, and their endorsement of impunity with regards to the crimes in question. This constitutes their endorsement and support of the crime in question.
A particular case arises when an individual offers an explanation of the events in question. That an individual offers an explanation of the events is of course not criminal; for instance, that specifically is what a defense attorney is paid to do: identify the most likely alternative explanations and present them as effectively as possible to the jury, so that if the jury is unconvinced, one can have high confidence in a guilty finding. However, when an individual begins to offer multiple explanations, especially those not obviously supported or those contradicted by evidence, of course the individual becomes an unreliable witness as to the truth of the matter. Hence, the individual cannot command any authority as to the innocence or the guilt of the accused, or as to the particular circumstances of the event.
Without any likely ability to state the facts of the matter or to contribute to the effective resolution of the investigation, the individual is not in any position to shield or defend the accused in question, or to deny access to facilities on the basis of justified true belief about the facts of the crime. By asserting such prerogatives and denying such access, an individual’s actions are not functionally distinguishable from indiscriminate obstruction of justice, hence the facilitation/conspiracy to commit the crimes in question with impunity.
Another situation arises when an individual asserts the authority to “interpret” (change) the law in a manner to excuse the crime in question, or to excuse it under a blanket statement (e.g. “national security”). Sometimes there are procedural considerations or ambiguities that present no-win situations for administrative and minor crimes. However, murder, rape, serious robbery, and facilitation of these and other just-law crimes do not present such ambiguities. Hence, in making this assertion, the officeholder asserts the impunity for just-law crimes, and once an official action is taken to further this approach, the officeholder becomes part of the conspiracy, even if the officeholder was not originally implicated in the crime.
A variant of this situation arises when a commander’s (not necessarily the supreme commander) subordinates are involved in a crime. You must convict/imprison/kill the individuals who ordered and funded criminal activity in order to stop said activity. If the commander orders an illegal action (such as kidnapping) and the result is a murder or other additional serious crime, if the commander then chooses to shield the perpetrators, the previous provision comes into play (note: the penalty for kidnapping and general criminal conspiracy applies to the commander in any case). The assertion of “only X was ordered and therefore I only can be responsible for X” is contradicted by the decision to provide aid and comfort to individuals reasonably accused of a different serious crime Y, even if all official documentation did support the original assertion. Because such individuals also were ordered out and funded by the commander, a continuation of said or similar policy after this impunity will result in impunity for future crimes. Hence if the commander continues the policy, the commander becomes directly supportive of such criminal behavior, and earns the corresponding reaction/punishment.