It is a discrete version of the Duffing equation. King, Kelly and Dan Kelly became involved in cattle duffing. In general, the Duffing equation does not admit an exact symbolic solution. The Duffing equation is an example of a dynamical system that exhibits chaotic behavior. Constable Fitzpatrick arrives at the Kelly house, to accuse Dan Kelly of cattle duffing. The Duffing map (also called as 'Holmes map') is a discrete-time dynamical system.