First of all, are these even wills? A handwritten, or holographic will does not come up in probate court very often, but whether or not it will actually count as a will depends on the state where this document was created. A holographic will is one that is handwritten and signed by the will-maker only, no witness signatures included.
So how does an executor know if they have come across a holographic will? One of the main hallmarks of this type of document is that it was clearly intended to be a will. This could mean something like the phrase or heading "here is my last will and testament", and the person's signature capping the whole paper off. Then the document might name someone as executor, and then further name beneficiaries.
As for state laws, they will vary greatly, but about a couple dozen states recognize holographic wills in their probate courts. The specifics in each state's courts could vary further of course. For example, in North Carolina, for a holographic will to be allowed in probate, the document had to be discovered in an area that was meant for safeguarding after the will-maker passed away. In other states, a will also has to have the date as well as a signature.
Then there are some states where holographic wills cannot be made within its borders, but their courts will still accept a holographic will if it was created in a state where holographic wills are recognized. These states include: Alabama, Connecticut, Delaware, Iowa, Minnesota, New Mexico, Rhode Island, South Carolina, and Washington. And then other states (Maryland, New York, and Rhode Island) sometimes accept holographic wills that were written by a person who wrote the will while they were a sailor at sea or a soldier in active fighting.
That being said, it can still be an uphill battle to prove that a holographic will is legitimate. These wills lack the standard authentication that comes from having witnesses sign the document. If anyone wants to contest a holographic will, their job will be much easier than with a normal will. To validate a holographic will, there needs to be witnesses who can provide testimony in court, saying that the will-maker had mentioned that the document was their will, that will-maker knew what they were doing, and that the paper was not made under pressure by a person who wanted to be named a beneficiary.
If you are the executor of someone's estate and you believe that a holographic will is valid, then you have to prove two things upon submitting this will to probate court. The first is that the will is totally or mostly written in the decedent's handwriting. So if the person wrote in the blanks of a template will, this usually does not count. Not only does the will have to be mostly handwritten, but you have to get witnesses who can swear to the fact that this handwriting and signature belong to the deceased person. These witnesses could be people who know the way the person wrote, and/or an expert analyst of handwriting.
Even if the document is in the deceased person's handwriting, you would have to further prove that the document was written with the purpose of serving as a will. This usually would be indicated by certain vocabulary (as previously mentioned), and through witness testimony.
In all matters of probate, an experienced attorney can help guide you through the maze of this complex area of law. As the legal process can become that much more complicated when a holographic will is involved, be sure to contact a probate lawyer today!