One reason a landlord can serve a Notice to Quit for Substantial Violation is when a tenant’s conduct “endangers the person of another”. The short definition of a substantial violation is any act that occurs on or near the property and endangers either a person or property. Endangerment does not necessarily require actual physical harm. The threat of physical harm (whether it be verbal or by gesture) can sometimes be enough. For example, a tenant that genuinely makes a manager or other resident afraid for their safety has committed a statutory substantial violation and can be served with a 3-day Notice to Quit. If a tenant doesn’t cause physical harm and the manager, staff, or resident is not actually threatened; you can serve a notice to quit for a substantial violation but may not (probably will not) prevail in court if the tenant contests the eviction. Even if a tenant’s behavior is not sufficiently serious to satisfy the statutory requirement for a “substantial violation”, the behavior may meet your lease requirements if you have crime free language (addendum in most cases), and almost always will support serving a three-day demand for compliance or possession. Any unlawful behavior is a violation of most leases and most unlawful behavior (and police response to it) represents an unreasonable disturbance of neighbors.