It is always good to have some form of will over no will at all, but a will that is not properly created may be just about as much trouble to resolve as having no will. At the very least, an improperly created will may leave itself necessarily vulnerable to legal challenges, which may result in a protracted legal battle that only serves to drain the resources of an estate and potentially ruin the interpersonal relationships of the family or community members involved in the conflict.
In order for a will to withstand scrutiny in court, its creator must have the legal right and capacity to create the document in the first place. A number of issues may prevent a person from legally creating his or her own will, such as the age or testamentary capacity of the creator, or his or her state of mind during the creation of the will. A person who is not yet 18 years of age may not generally create a will, for instance, and a person who is not legally of sound mind or who creates a will under duress from some other party may see the will tossed out or easily challenged.
Even if a will is created by an individual of sound mind, proper age and without undue influence, it may not withstand scrutiny or challenges if it was not properly created in the first place. Most commonly, wills face challenges if they do not comply with the laws that govern estate planning or taxation, or were not signed in the presence of two disinterested parties serving as legal witnesses. Disinterested parties may not benefit from the terms of will.
If you have concerns about your own will or a will that involves your interests, you can consult with an experienced estate planning attorney to ensure that you fully understand the issues at hand in your specific circumstances. Do not underestimate the value of a careful, detailed understanding of a will and the laws that govern it.
Source: FindLaw, "What Is a 'Valid Will'?," accessed March 23, 2018