To produce short X-ray pulses for SwissFEL(1), it is necessary to compress the electron bunches by a factor of 300, down to sub-fs for the attosecond operational modes. To achieve stable EEL output accurate timing of the initial electron injection at the main linear accelerator is necessary. Tolerance studies show, that to reach the final performance goals, less than 40 fs relative rms jitter is required from the electron gun, relative to the reference. Here we present independent residual RF phase noise measurements of the laser oscillators, showing an exceptional similar to 30 fs integrated rms jitter. Moreover timing studies at the SwissFEL Injector Test Facility, based on charge detection at the sharp rising edge of the Schottky-scan were performed allowing for systematic correlation studies and showing a residual jitter of similar to 150 fs at 10 Hz from the pulsed laser system and beam transport respect to the reference. For future development, available relative jitter measurement techniques for pulsed laser systems will be reviewed and their applicability for laser arrival time monitoring and feedback for EEL applications will be discussed. (C) 2013 Published by Elsevier B.V.