  We present results from a blind, spectroscopic search for redshift 5.7 LyA
emission-line galaxies at Keck I. Using a band-limiting filter and custom
slitmask, the LRIS detector was covered with low resolution spectra in the 8100
- 8250 A atmospheric window which contains no bright night sky emission lines.
Nine objects with line fluxes greater than our flux limit of 6e-18 erg/s/cm2
were found in the ~5.1 square arcminute field. Follow up observations indicate
none of these are z=5.7 LyA emitters -- a result which places strong limits on
evolution scenarios for LyA emitters between redshift 3 and redshift 5.7. In
particular, the paucity of z=5.7 LyA emitters raises the question of whether
the LyA -selected population plays a significant role in maintaining the
ionization of the intergalactic medium at z = 5.7.
  We argue that if the escape fraction of LyA from galaxies is less than $0.4
f_{LyC}$, where $f_{LyC}$ is the escape fraction of Lyman continuum photons,
then the star formation rate in the \lya emitting population is high enough in
the no-evolution model (our upper limit) to maintain the ionization of the IGM
at z=5.7.
