Accessible CAT$(-1)$ groups of critical exponent less than one

Let $X$ be proper CAT$(-1)$ and let $Γ\le\Isom(X)$ be finitely generated and discrete. The sharp structural theorem states that, if $Γ$ is accessible over finite subgroups and $δ_X(Γ)<1$, then $Γ$ is geometrically finite and virtually free, has a finite graph of groups with finite edge groups and vi