The short answer is that GENERALLY accounts/policies with beneficiary designations get distributed according to those designations, regardless of what the will says. But there are exceptions to every rule. For instance, if the beneficiary named on the account is deceased, that can change things.
The other attorney is correct about the general rule. Exceptions may include provisions in the will that joint accounts are for convenience only or outside evidence that the intent of the decedent was to have joint accounts distributed according to the will.
Joint accounts with the right of survivorship, generally go to the remaining owners living. That means the survivors of the deceased pervious will not recieve their ancestors share. It the accounts were joint, without a survivorship contingency, the heirs of the previously deceased party will take. I would suggest engaging an attorney and receiving an opinion it is rational to rely upon.
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I would generally agree with the prior answers. Michigan law presumes that joint accounts pass to the survivor. The contesting party would need to prove that that was not the intent, and even then, she might not win. I would also point out that the items you mentioned are all "tangible personal property." Items like this are not mentioned in the Will because the Will does not control them or affect the distribution of them upon death. Unless there is a statement in the Will that provides that the "jointly held assets are held that way merely for convenience," then I think the survivors have nothing to worry about. As for the accounts with beneficiaries, I have only seen something like that set aside is the beneficiary is an ex-spouse that specifically waived that asset in the divorce. I think that the heirs are out of luck, when it comes to these assets.
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Generally joint accounts go to the survivor outside probate. The will applies to assets in probate, generally speaking. See exceptions as noted by other attorneys. A full reading of the will by an attorney is advised.
This answer is not specific legal advise. No attorney client relationship has been established. It is general commentary on the question presented, without the benefit of a full disclosure of all relevant facts. Seek an in-person consultation with a licensed professional.