It depends on the necromancy.

Most forms of necromancy create a being under the control of their necromancer. In that case, the dead’s testimony would be worthless as the dead would be under the complete control of another.

GURPS Technomancer is a modern setting with magic, including necromancy, ever since 1945. In some (red) States you can be sentenced to life in prison/death plus years of hard labor. Even your undead corpse is put to use clearing trash off the side of the road for 20 years.

Only by gov’t-licensed necromancers, otherwise there’s a risk of witness tampering.

What recourse would there be against perjury?

I think the most reasonable interpretation is that the law doesn’t currently recognize the undead as being people, let alone being the same person they were in life. It would need to be shown to be a reliable source of evidence, similar to any new technology that claims to offer insight into a case. A random judge might allow it, but it would be easy grounds for an appeal if it can’t be shown to do exactly what it claims to do.

DNA evidence was new once, but so was the polygraph. Only one of these is admissible, and for good reason.

Eyewitness testimony is notoriously unreliable. I’d imagine that it would only get worse without the eyes.

Heh, this is a question addressed in fiction some.

There’s a qri, Laurell K Hamilton, that has a character that’s a necromancer that raises zombies for legal issues as part of her job.

And, while it may seem derivative (and I admit it is to a degree), My urban fantasy series is based around a forensic necromancer, who raises spirits, zombies, and otherwise applies his magic to legal issues.

Back in the day, I spent a couple years talking to cops, lawyers, and a few medical examiners in preparation for doing writing. I used that to address their objections to the idea in my stuff.

But, yeah, if certain barriers could be overcome, courts could accept testimony from an undead entity. It would likely end up appealed and chained challenged up to the top court in any given country, bit it’s possible

It would depend on the type of necromancy, but at the end of the day, I think it would still be a conflict of interest since the person bringing them back would have great say, unless they are considered some type of expert witness necromancer.

Necromancy is the practice of magic involving communication with the dead by summoning their spirits as apparitions or visions for the purpose of divination; imparting the means to foretell future events and discover hidden knowledge.

The necromancer’s capacity to create minions and command them to fight for him or her is generally enough to satisfy even the most critical of viewers. As necromancers might easily be termed one-person armies, they are usually compelling and feared. The fact that they dabble in magic and the supernatural does not help their image as upstanding citizens.

What type of necromancy is being used. If it’s from Dungeons & Dragons Fifth edition, you only get to ask them like 5 questions, and they don’t have to answer you. They can also potentially lie.

What do you mean by “possible”? Most jurisdictions have a law against interfering with the dead / a corpse, and necromancy, while suddenly possible would therefore remain highly illegal.

Even if legalised, consider how often difficult decisions have to be made about whether to exhume a corpse to seek evidence of some sort. I can’t imagine it would be any easier to decide to have a corpse resurrected.

Habeas corpus takes on an entirely different bent, for sure.

There’s also the state of mind of someone who has been resurrected to take into account as well. There they were in oblivion or eternal rest or whatever it is that the dead experience and suddenly they’re dragged back to this mortal coil with thoughts, feelings and the knowledge they’ve been dead for a long time, and there’s living people who haven’t been through any of that throwing questions at them left, right and centre.

If it happened often enough, advocacy groups for the unwillingly resurrected would be set up. And more people would opt for cremation.

The undead listen to a much higher authority than any mortal court. But that doesn’t stop the court from trying to summon them, but they might need a warrant wielding warlock to make it happen.

Going sci-fi, but I think I remember there being a thing in the altered carbon books that kind of relates to this.

In that series most people have a device implanted that can store their consciousness, it can be backed up, etc. if you die your consciousness can be uploaded to a new body, maybe a clone of your own, maybe another spare body no one was using. They get around long space flights by just sending the stored consciousness into a new body at the destination, prisoners can be uploaded to storage and their bodies used elsewhere, etc. and the only way to reliably kill someone is to destroy that device, and if they’re rich enough they may have a remote backup so even that isn’t a guarantee.

So murder victims are routinely uploaded into new bodies to testify at their own murder trials.

Catholics oppose this though, they believe that your soul is separate from your consciousness and can’t be stored in that device, backed up, etc. and so to respect their religious rights they can’t be popped into a new body to testify.

I imagine that necromancy would have the same and probably stronger opposition from a lot of religious people and we’d run into the same kind of legal issues.

https://youtu.be/N6hVmn9FM7o

Judging from the movie Rashomon, it wouldn’t actually resolve anything.

I’m not a lawyer, but let’s have some fun with this.

To start, I’m going to have to assume a jurisdiction. I’ll go with California, because Hollywood films have depicted a lot of walking dead, zombies, and whatnot. And also because that’s the jurisdiction I’m most familiar with. I think that such a case where the undead might be a witness would mostly arise in California state courts, since zombies rarely walk/jump/crawl quickly enough to cross state lines from the major population centers of California, which wokld invoke federal jurisdiction.

Now, we need to hone in on the type of case. A murder case where the victim is called as a witness would certainly be very juicy. But the same legal intrigue would arise from a less-interesting inheritance or family law case. We could also go into contracts and see whether or not the presence of an undead counts as an “act of God” but maybe that’s a bit too niche and law-school theoretical.

To really showcase the problems this would pose to the court, we will focus on the undead being witness in a criminal trial, as the standard of proof to convict the defendant would be proof “beyond a reasonable doubt”. As the most stringent category of proof, it necessarily follows that the court must err on the side of the defendant in matters of impartiality. This is because the court is technically an arm of the state, and the prosecution wields all the resources of the state against an individual who stands accused of some criminal act.

As such, for criminal trials, there are certain constitutional rights of the defendant that the court must uphold. The foremost is the right to due process, guaranteed by the Fifth and Fourteenth Amendments. One of the results from applying due process is that evidence introduced in a criminal trial must not be “unduly prejudicial”. That is, no evidence can be admitted which so irresponsibly causes the jury to render a verdict based on anything but the law.

Often, this rule is invoked to set aside irrelevant evidence which has no bearing on the charges, except maybe to impune the reputation of the defendant so that the jury thinks they’re a terrible person. Other times, it can be used to exclude relevant but really-bad evidence. The US courts have been through cycles where novel science is used in a prosecution but which later turns out to be bunk and lacking any foundation in reality. It certainly is “evidence” but because it purports to be science when it’s really not, it must be excluded. Psychics are certainly not going to be welcomed witnesses as a subject matter of expert.

Finally, the other category for evidence being unduly prejudicial is when the jury – through no fault of their own – would weigh that evidence as being the primary factor, above all else, whether it’s DNA or video evidence. This is more a matter of testimony evidence rather than physical evidence. Imagine a small, devoutly religious town where the local pastor is called to testify about whether the defendant could have committed hit-and-run.

Having a respected community authority figure testify about someone’s potential to commit a crime might be something the jury members would be open to hearing, but the judge might have to weigh whether the fact the fact that the lay witness is a pastor will cause the jury to put too much weight on that testimony. If there are other ways to obtain the same evidence – such as bringing in the defendant’s mother or employer – the judge should not allow the pastor to testify, because it could jeopardize the soundness of the trial and lead to an appeal.

So now we come back to zombies. Would a jury be able to set aside their shock, horror, and awe about a zombie in court that they could focus on being the finder of fact? If a zombie says they’re an eye-witness to a mugging, would their lack of actual eyeballs confuse the jury? Even more confusing would be a zombie that is testifying as an expert witness. Does their subject matter need to be recent? What if the case needs an expert on 17th Century Parisian fashion and the undead is from that era? Are there no fashion historians who could provide similar expert opinions?

But supposing we did overcome all that, there might be one form of testimony which – even though very prejudicial – might be allowable for a lay-witness (ie not expert) zombie witness could testify about, and I already mentioned it earlier.

In most jurisdictions and in California, a dying person’s last act which might point to their killer will not necessarily be excluded for being irrelevant or being circumstantial. It is a rebuttable presumption that someone dying has no incentive to lie, and will likely have been the final witness to their own murder.

To that end, it’s entirely plausible that a zombie who died by murder could come to court to testify against their killer. Of course, how long does it take for the dead to become undead? If this takes longer than the statue of limitations allows, the defendant would walk. Likewise, if the zombie’s testimony is the only shred of evidence for the murder, that’s not likely to convince the jury. Not unless, of course, the details of the testimony match the circumstances of the crime so well that it wasn’t a fluke.

TL;DR: rules of evidence would still apply to the undead, and judges must take care to balance the probative value of evidence with any prejudicial quality it may carry.