Part of the issue here is terminological. Inferences, at least in the ordinary sense of the term, are things that happen in the minds of rational agents. An agent believes some A, or maybe some A, B, C, ..., and considers that this provides a ground, reason, or justification for accepting Z, and so can be said to infer Z from the given premises. So, inferences are made by individuals and as such are subjective.
One rational agent may attach more weight to some premise than another agent, or may believe that some premise is too unlikely to be plausible, or may judge that it is more likely that the conclusion is false than that all the premises are true. In the context of a jury, some jurors may be more swayed by a convincing testimony than others, while others might give more weight to physical evidence. Some might disregard forensic evidence if they don't understand it. Some might choose to ignore a witness if they believe the witness lacks credibility. Even if the jurors agree on the evidence, they may differ in whether it justifies a verdict beyond reasonable doubt.
However, the term inference is often used within logic to refer to a formal deduction. Logicians use the term rule of inference to refer to the rules of a formal system that allow one proposition to be deduced from others. Such rules are not subjective in nature: the rules of a logic apply without exception. This terminology is unfortunate and several logicians, such as Gilbert Harman, have long argued that we should drop the term rule of inference and replace it with rule of implication. Logicians learned over a hundred years ago to separate logic from psychology, but the use of inference in this way is a hangover.
So, if by inference you mean the activity of rational agent in coming to believe something on the grounds of other beliefs, then inferences are typically subjective. Even if you use formal logic to deduce B from A, the logic itself will not tell you whether it is more plausible to believe both or to believe neither. This is sometimes expressed by the phrase: one person's modus ponens is another person's modus tollens.
On the other hand, if you follow the convention of using inference to mean a logical deduction, then there are agreed standards for such things. However, deduction is not the only kind of inference. There is abductive and inductive reasoning, there is reasoning by analogy, statisitical inference, etc. The kind of reasoning that occurs in a courtroom is often of the abductive kind. A criminal case might be concerned with establishing whether the guilt of the defendant provides the best explanation of the evidence.