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For domestic violence, sexual assault, and stalking, abusive partners can misuse messaging to harass, intimidate, and threaten.

How significant is evidence of messages in a messaging application (like WhatsApp) considered in this case, assuming there is little to no other circumstantial evidence?

I am a computer science researcher and studying the deniability property of messaging applications. The deniability property of messaging ensures that if Alice and Bob communicate over messaging applications, neither of them can prove cryptographically to a third-party who sent which message. Both parties can forge each other's messages without leaving any trace. For my research, I am trying to understand if the messaging applications are being used as evidence and to what extent. Could it be possible to put a false accusation on someone just based on the messaging application? And how do cyber law specific to this differ from state to state? Any pointers to other resources would be helpful too.

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    NB: In Austria, there is currently a government crisis and corruption investigation (just) because of WhatsApp messages found (by accident) on the cell phone of a high government official.
    – Heinzi
    Oct 8 at 12:15
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    Possibly relevant, within the United States, there were some cases involving whether keeping a chat log was considered to be "recording a conversation without the permission of all parties" and, IIRC, if the application defaulted to logging, it was allowable, but it was not if that was not the default. Around that time, a bunch of apps started defaulting to not logging. Oct 8 at 14:48
  • @Heinzi that sounds interesting. Can you point me to any resources where I can read more about that investigation?
    – tarun14110
    Oct 8 at 15:19
  • @tarun14110: It's all over the media here, but, unfortunately, all local media are German. The Wikipedia entry has a few English-language references which might be good starting points: en.wikipedia.org/wiki/Sebastian_Kurz#Corruption_inquiry.
    – Heinzi
    Oct 8 at 15:35
  • When you say "state to state" I guess that's a clue that you're talking about the USA? Oct 8 at 20:42
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Messaging (and other online communication) are fixed media.

A face-to-face conversation, or a telephone call, does not exist at all - except in the mental recollections of the participants. And those are always very problematic as evidence, because people's recall is inaccurate.

Whereas communication in a fixed medium is durable: a newspaper, a sound recording, security camera footage. It stands on its own and can be examined by experts.

What catches a lot of people off guard about the Internet is they are mostly fixed media.

Prior to the Internet, investigation of harassment almost entirely depended on anecdotal evidence. It was difficult to prosecute cases which were entirely based on the victim's word. The closest any of this came to objective evidence was a polygraph, and that wasn't reliable. Of course we want bona-fide victims protected, but what keeps a malicious actor from putting someone else in jail with words alone?

Now with the Internet, much of the evidence is rendered in fixed media. This is a "breath of fresh air" for such prosecutions!

However, just like any other physical evidence, it must be brought into evidence by the testimony of persons, and that testimony gets to be cross-examined. And this is where your concerns about provenance get addressed. A party will assert that the messages are forged, and that will be examined.

The validity of evidence is itself on trial.

There are two evaluations: first whether the evidence is even valid enough to present to a jury, and evidence that makes the cut is then examined and cross-examined in front of the jury.

Keep in mind that contrary to TV drama, there's no "surprise evidence". Almost any evidence - and certainly ALL evidence in a fixed medium - must be shared with the other party long before trial. Pre-trial, it will be challenged, the phone/device subpoenaed and turned over to experts for analysis. If it is evident that the party "has conveniently deleted or lost" the material, the evidence will be thrown out. And if the party is proven to have falsified the data, they're in much worse shape.

A lot of chat services keep chat logs on the server/cloud, in the clear. Getting those is as easy as subpoenaing them, and that will be a canonical answer because the ISP would have no reason to lie.

For a service where chat logs are kept in the clear only by individuals who choose to keep them, then "reading those logs into evidence" will involve a cross-examination of the parties involved as to their honesty and motivations.

I don't know what and how WhatsApp stores when they log chats, so I don't know if there's any cryptographic information there that could be authenticated. But certainly if "he" presents one chat log, and "she" presents a different chat log, then we're clear around to "he said, she said". But all of it together can be examined.

For instance, linguists can look at other chats, discern the writing styles of each party, and then look at the disputed lines and examine who is more likely to have written those. And they give testimony on that.

So it is evidence, but it gets two rounds of possible challenge: First as to whether the evidence is reliable enough to even present to the jury, and then experts testifying in front of the jury their opinion of its reliability.

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    A big thing is proving the person accused sent the messages, vs someone else with access
    – Tim
    Oct 9 at 9:59
  • WhatsApp messages (and many other messaging services) are end to end encrypted, which means that AFAIK they cannot be logged by WhatsApp and WhatsApp only stores metadata related to who sent a message to whom and when. As far as I know there is also no way to edit these messages, not even locally, because they're stored encrypted as well. there used to be ways to change them using third party software, but those apps required root access.
    – Nzall
    Oct 9 at 19:05
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    @Nzall They COULD be logged by WhatsApp, they just can't be decoded or validated without at least one party sharing their private key and whatever public keys they have. I presume this would be a case where the accuser entered into evidence a plain text chat log, and NOT the underlying encrypted data. When you subpoena it, they don't have it (and are hoping you don't have it either). Oct 9 at 19:29
  • In addition, many phones (Android and iOs) automatically back up data. While that storage is itself encrypted (hopefully...) by virtue of it being possible to restore to a new phone (the usual use case after phone lost or stolen or replaced with the latest model) it could mean that data deleted from the phone may actually be available "in the cloud". Gets to a legal issue of how/when/why the cloud provider is required to hand over that information. Oct 10 at 1:31
  • @Tim yep. I had someone break into my house, take stuff, then text me taunting me about it. I called the cops and they said he could claim someone else sent it and wouldn't even arrest him. (USA)
    – Kat
    Oct 10 at 18:13
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Can messages in messaging application be used as evidence to accuse someone?

When you say "accuse" I assume you mean have enough evidence to support a prosecution, as anyone can accuse anyone of anything, so I will answer in that vein from the perspective of .

A major tool in the law enforcement armoury is cell site analysis which can geo-locate a phone etc quite precisely. This coupled with other evidence such as CCTV, records of banking transactions, and ANPR may be able to create what is sometimes colloquially referred to as a "jigsaw identification" to show who was (and was not) in the vicinity of the phone when the offending messages were sent. It is then a matter for the jury to consider the weight of this evidence, and any defences put forward, to determine who sent what to whom.

The messages themselves will be evidence of, for example, offences contrary to the Malicious Communications Act 1988.

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