Legal Definitions - diligentia

Diligentia is a Latin term originating from Roman law that refers to the concept of carefulness or diligence. It describes the level of attention, prudence, and effort a person is expected to exercise in a particular situation, especially when they have a duty to look after someone else's interests, property, or well-being. The failure to meet the required standard of diligentia can lead to legal responsibility for any resulting harm or loss.

Roman law recognized different standards of diligentia, reflecting varying expectations of care based on the context and the relationship between the parties:

• Higher Standard (diligentia exacta or diligentia boni patrisfamilias): This standard demands an exceptionally high level of care, equivalent to the prudence and attention that a highly responsible and capable head of a household would typically apply to their own most important affairs. If someone is held to this standard, they can be liable even for slight negligence, meaning a minor oversight that a very careful person would have avoided.
• Lower Standard (diligentia quam suis rebus): This standard requires a person to exercise the same level of care that they ordinarily apply to their own affairs. It's a more personal and concrete measure. If a person generally takes good care of their own things, that's the standard they are expected to meet. If they are typically less careful with their own possessions, that lower (but still reasonable) level of care might be acceptable, provided it doesn't fall into gross negligence.

Examples:

• Example 1 (Higher Standard):

  Imagine a professional investment manager who is entrusted with a client's entire retirement savings portfolio. This manager is expected to exercise diligentia exacta. This means they must not only follow all regulations and industry best practices but also proactively research market trends, diversify investments prudently, and monitor the portfolio with the same extraordinary vigilance a highly responsible individual would apply to their own most critical financial assets. If the portfolio suffers significant losses due to a minor oversight or a failure to anticipate a foreseeable risk that a highly diligent professional would have identified, the manager could be held liable.

  This illustrates diligentia exacta because the investment manager is held to an objective, very high standard of care, reflecting the immense value of the entrusted assets and their professional duty.

• Example 2 (Lower Standard):

  Consider a scenario where a neighbor asks you to borrow your lawnmower. You agree, and they promise to return it in the same condition. The expectation here would likely be diligentia quam suis rebus. Your neighbor is expected to use and care for your lawnmower with the same level of attention and caution they would typically apply to their own lawnmower. If they accidentally leave it out in a light rain shower, which they sometimes do with their own tools without causing damage, it might not be considered a failure of diligentia. However, if they habitually leave their own tools exposed to harsh weather, and they do the same with yours, causing significant rust and damage, they could be found to have failed in their duty, as they didn't even meet their own normal standard of care in a way that caused harm.

  This demonstrates diligentia quam suis rebus because the standard of care is measured against the neighbor's personal, usual level of attentiveness to their own property, rather than an abstract ideal of a "perfect tool owner."

• Example 3 (Higher Standard in a Professional Context):

  A pharmaceutical company is developing a new drug. In this critical process, the company and its scientists are expected to apply diligentia exacta. This involves meticulously following all scientific protocols, conducting extensive clinical trials, rigorously documenting every step, and proactively identifying and mitigating any potential risks to patient safety, just as a highly responsible entity would protect its own reputation and the well-being of its stakeholders. If the drug later causes unforeseen side effects due to a minor oversight in testing or a failure to thoroughly analyze data that a highly diligent research team would have caught, the company could be held responsible for failing to meet this elevated standard of care.

  This example highlights diligentia exacta by showing how a professional entity, dealing with public health and safety, is expected to demonstrate an exceptionally high and proactive level of care.