Sufficient evidence to prove the existence of ghosts does not exist. Scientifically, this alone cannot be used as concrete proof that ghosts do not exist, but rather it provides two possible evidence-based conclusions. Either ghosts do not exist or the procedures used to gather evidence are not up to the task.
From a scientific perspective, no amount of evidence can prove the non-existence of something. In the case of ghosts, this leaves much of the story up to the individual to interpret and formulate their own belief or theory. Unfortunately, the evidence presented in favor of the existence of ghosts can be quite compelling to an individual lacking the expertise to provide an objective appraisal of that evidence.
Many people are in such a hurry to believe that it takes very little of this so-called evidence to convince them. Others may present a skeptical front, but when confronted with something they are unable to explain, they will quickly accept the explanation which seems most logical at the time. Given these factors, it can be inferred that either ghosts are being described by individuals who lack sufficient objectivity and education to accurately document their experiences or the tools and equipment being used to gather evidence are not capable of doing so.