#1 - The will wasn't signed in accordance with applicable state laws.
Each state has very specific laws governing how a Last Will and Testament must be signed. For example, in Florida a will must be signed by the Testator in the presence and hearing of two witnesses. In other words, the Testator and two witnesses must be in the same room at the same time and each must sign the will while the others are watching. And while it's easy to assume that a will executed in an estate lawyer's office is signed with the proper legal formalities, in reality this isn't always the case. Thus, failing to sign a will in accordance with applicable state laws is the first and foremost reason why a will is contested and also the most common reason why a will is found to be invalid.
#2 - The Testator lacked testamentary capacity to sign a will.
Testamentary capacity involves the following: The Testator understands (1) the nature and value of his or her "bounty" (assets); (2) the natural objects of that bounty (who should logically inherit the assets); and (3) the legal effect of signing a will. State laws dictate the threshold that must be overcome to prove that a Testator lacked testamentary capacity and usually the bar isn't set very high. For example, in Florida a person can show signs of dementia and yet still have the testamentary capacity to sign a will. Thus, the testimony of the witnesses to the will signing becomes crucial, and absent a doctor's visit or an adjudication of incapacity within days of the will signing, lack of testamentary capacity is difficult to prove.
#3 - The Testator was unduly influenced into signing a will.
As people age they become weaker both physically and mentally and therefore more susceptible to the influence of others. The key to undue influence in the context of a will contest is did the alleged undue influencer exert such extreme pressure and put the Testator under severe duress so as to cause the Testator to lose free will and instead succumb to the will of the alleged undue influencer? And mere nagging, threats and verbal abuse aren't enough, it takes much more, such as consulting with the Testator's attorney on the provisions of the will, paying for the will, holding the original will in safekeeping, and isolating the Testator from family and friends. As with lack of testamentary capacity, undue influence is difficult to prove.
#4 - The will was procured by fraud.
A will procured by fraud is one that the Testator is tricked into signing. For example, if the Testator is presented with a document that the Testator thinks is a deed or power of attorney but is really a will and the Testator signs it, then the will was procured by fraud. The problem with proving that a will was procured by fraud is that the Testator can't be questioned about what was signed. This is where state laws come into to play - the witnesses will need to be asked what they thought the Testator was signing and why they were asked to serve as witnesses. And if the testimony of the witnesses doesn't add up, then the will may be declared invalid because it wasn't signed properly, not necessarily because it was procured by fraud.
Do you still think you want to contest a loved one's will?
If after reading the four legal grounds for contesting a will you still think you have legitimate reasons for challenging the validity of a loved one's will, think again. In the absence of blatant lies and wrongdoing on the part of multiple people, or explicit medical evidence at or near the time the will was signed that the Testator was incompetent, proving that a will is invalid is difficult and expensive.