In Florida, the seminal case is Carpenter v. Carpenter, 253 So. 2d 697 (Fla. 1971).  In that case and cases which have followed there from, the Court looks to claims of undue influence and considers the factors of the presence of the beneficiary at the execution of the will, the presence of the beneficiary on the occasions where the donor expressed a desire to draft the instrument, knowledge of the contents of the instrument before its execution, providing instructions on the preparation of the instrument, the beneficiary‚Äôs securing of witnesses for the execution of the will and the beneficiary's safekeeping of the executed instrument.

Undue influence can be indicated where there is a fiduciary relationship between the testator and the undue influencer.  Jordan v. Growney, 416 So. 2d 24 (Fla. 4th DCA 1982) or where the execution of a will or trust is kept secret from other prospective beneficiaries by the undue influencer.   Estate of Burton, 45 So. 2d 873 (Fla. 1950).

The validity of a last will and testament can be denied where the weak mental or physical health of the testator is at issue.  Estate of Reid, 138 So. 2d 342 (Fla. 3rd DCA 1962) or where there is a dramatic change displayed in the new will in question as opposed to the former testamentary plan of the decedent.  Newman v. Smith, 77 Fla.377, 149 S. 186 (Fla. 1932).

While the lack of testamentary capacity can be alleged in a will contest petition, this plan of attack is sparingly utilized since there is a relatively low threshold of mental capacity needed to execute a will.  Smith v. Clements, 154 So. 520 (Fla. 1934); American Red Cross v. Estate of Jaynesworth, 708 S. 2d 602, (Fla. 3d DCA 1998).

In fact, the burden to establish incapacity on the part of the testator is a difficult one.  In Hendershaw v. Estate of Hendershaw, 763 So. 2d 482 (Fla. 4th DCA 2000),  the court found that the contestant needed to show that the testator lacked capacity on the day of the execution of the will and not just a showing of incapacity on other days.