FANYIE AND OTHERS v. LAMPTEY Landlord and tenant—Customary tenancy—Abunu and abusa tenancies—Burden of proof—Dispute between plaintiff-tenants and defendant-landlord as to nature of customary tenancy—Nature of burden on plaintiff to prove abusa tenancy—Admissions by defendant relieving plaintiff of burden—Whether burden of persuasion shifting to defendant to establish abunu tenancy.