Pain radiating along the path of the sciatic nerve. Decreased internal rotation of femur.
Some clients will feel a stitching pain in the area of the inguinal ligament when stretched this way (an indication they need their psoas stretched - technique 3 and technique 39). If this is the case you may do the stretch with their foot placed medial to the opposite knee instead of lateral.
Other Psoas stetches can be found on the Psoas page.
Usually sciatica is caused by a tight piriformis muscle pressing on sciatic nerve.
Check internal rotation of legs by holding legs above the ankles and turning feet inwards. Take foot of tight side and place it lateral to opposite knee. Stroke piriformis while it is stretched, going from the greater trochanter to the sacrum using the heel of your hand. Recheck internal rotation of legs. You may work up the erector spinae muscles from L5 to T1 on the side closest to you while your client is stretched out.
A more specific stretch of the piriformis can be done by holding the ASIS down while pressing the clients knee away from yourself. See Piriformis Stretch - Hand on ASIS.