Afaik this technically impossible with Apple Health at this point.
> Many people with limited funds for expensive lawyers will plea bargain for 2 years
Plea bargains rarely (if ever) happen in the Netherlands, and I suspect they don't in Germany either. The reasoning behind this is probably that when the state sues they should go for justice, not victory. Plea bargains may incentivize strong arming, bluffing tactics and money politics that don't belong in a court room.
That was long a problem with DNA data.
I don't know how completely they test DNA nowadays in criminal cases, but in the early days and for many many years afterwards the tests did not determine a unique individual. It just narrowed it down. There could be a large number of people in the world that would match the sample.
There were two correct ways to use DNA with that level of matching.
1. After you have narrowed down your list of suspects through ordinary, non-DNA police work to a small number of good suspects, then check their DNA. If exactly one suspect matches it is extremely likely that is the correct suspect.
2. It can be used to nearly conclusively eliminate suspects. (I say "nearly conclusively" because you are almost never sure that the DNA you are testing from the crime scene is actually from the criminal. There are almost always ways someone who was not the criminal could have left DNA at a crime scene).
Then there was the completely wrong way to use it, which, unfortunately WAS often used:
• Keep a database of DNA samples from a small subset of the general population, such as people who have been arrested. When you start investigating a crime and think you have a DNA sample of the criminal, check that against your database, and if you get a single match conclude that person was involved.
This approach of starting by looking up DNA from the crime scene in your database and focusing everything on a single match is only valid if:
A) the database includes everyone who could possibly be the criminal, or
B) your DNA test is comprehensive enough that it does identify people uniquely.
We don't do A yet, and as I said I don't know if the test they use nowadays are good enough to satisfy B.
The DA says, “there’s a million-to-one chance it wasn’t this dude.”
Without any other evidence linking the purported perp to the crime, the reality is that the DNA only shows he’s one of 350 people who could have done it (assuming a population of 350m).
To be clear, this would not be possible on iOS, because the data is stored locally on the device (They had access to it). Health data cannot be remotely queried.
I accept that a lot of this idea in my head is from films set in the USA but then again I have read on the subject and plea deals seem to be not only accepted but encouraged.
How a person, who seemed to have murdered someone, ought to be given only M years of sentence just because that person agrees for a plea deal where if properly tried and proven guilty the person might have been sentenced for N years which usually would be more than M? Just because the prosecution have to work less the culprit gets a lesser sentence? And as you say many who are arrested and haven't done anything but just wants to live with a lesser sentence just agree to such deals because they can't afford a lawyer, let alone a good lawyer.
Is it not questioned? Is it something in the constitution? How does it work? The "deal" itself - is it verbal or plea deals are actually signed and verified?
The deal is in writing.
As you allude, though, it's a terrible system. The DA deliberately files charges one or two tiers higher than needed as a scare tactic to encourage defendants to plea out.
The motivation seems mostly to keep the number of actual trials down to match the capacity of the overall system. And it's one of the reasons (there are others) that our incarceration percentage is higher than anyone else's.
For DNA testing, for example, the testing labs don't publish, and the courts do not allow questions regarding, their base rate false positive rate. They're worried that juries wouldn't be able to reconcile the "0.5% of DNA tests are false positives" with "beyond a reasonable doubt".
If you don't know the false positive rate, and someone comes in with a positive test result, you know almost nothing conclusive.
This type of use would be very troubling to everyone because, given enough N value, you can always find some people to fit a criteria. Then, it becomes a matter of making a case that fits very narrow criteria. Hard to defend against, possibly very expensive to defend against.
Now, in the US, for these types of cases you need to prove beyond a reasonable doubt. But in reality, many people with limited funds for expensive lawyers, when faced with 30year sentences, will just plea bargain for 2 years -- which is not something that needs proof beyond a reasonable doubt.
In summary, using phone data to independently support an already strong case might be a good way to set innocent people free. Using phone data to find culprits might be a great way to innocent people to get a false accusation just based on statistics and the laws of querying on large datasets.