Kechris's first conjecture on projective unreachable cardinals

Let ${\mathbf{\delta}}^1_{2n+2}$ denote the supremum of the lengths of ${\mathbf{\Delta}}^1_{2n+2}$ pre-well-orderings of ${\mathbb{R}}$. Assume ${\sf{ZF+AD+DC}}$. Kechris's first conjecture. Then ${\mathbf{\delta}}^1_{2n+2}$ is ${\mathbf{\Delta}}^1_{2n+2}$-unreachable. Jackson subsequently proved this conjecture, using his computation of the projective ordinals and the strong partition property of ${\mathbf{\delta}}^1_{2n+1}$, so the statement is solved.