Insurance companies and defense lawyers often use this phrase to argue that a hazard was "open and obvious" and that the injured person should have seen it anyway. In plain terms, inadequate lighting means there was not enough light, or the light was placed badly enough, that a reasonably careful person could not safely detect changes in walking surface, stairs, edges, obstacles, spills, tools, or other dangers. The issue is not total darkness alone. Glare, burned-out bulbs, shadowed stair treads, unlit entrances, and lighting that fails during normal use can all qualify.

In a premises liability claim, lighting matters because it affects whether a property owner exercised reasonable care. Poor illumination can turn an ordinary condition into a hidden danger. Photos, maintenance logs, incident reports, bulb-replacement records, and measurements taken soon after the event can help show whether the condition was unsafe. Medical records from facilities such as Concord Hospital or Elliot Hospital in Manchester may also help connect a fall or strike injury to the event.

In New Hampshire, inadequate lighting can affect both negligence and comparative fault. Under RSA 507:7-d, a claimant whose fault is greater than 50% is barred from recovery; otherwise damages are reduced by that percentage. A defense claim that "you should have seen it" is often aimed at that threshold. Most personal injury lawsuits must be filed within 3 years under RSA 508:4, I.