  This paper is concerned with the analysis and implementation of robust finite
element approximation methods for mixed formulations of linear elasticity
problems where the elastic solid is almost incompressible. Several novel a
posteriori error estimators for the energy norm of the finite element error are
proposed and analysed. We establish upper and lower bounds for the energy error
in terms of the proposed error estimators and prove that the constants in the
bounds are independent of the Lam\'{e} coefficients: thus the proposed
estimators are robust in the incompressible limit. Numerical results are
presented that validate the theoretical estimates. The software used to
generate these results is available online.
