25 Del. C. § 5903: Defenses.

It shall be sufficient defense to this proceeding, if any defendant of record establishes that:

(1) The condition or conditions described in the petition do not exist at the time of trial; or

(2) The condition or conditions alleged in the petition have been caused by the wilful or grossly negligent acts of 1 or more of the petitioning tenants or members of the tenant’s or tenants’ families or by other persons on the premises with the tenant’s or tenants’ consent; or

(3) Such condition or conditions would have been corrected, were it not for the refusal by any petitioner to allow reasonable access.