I might place a weight lifting session before a speed session in the following circumstances:
1. When I want to emphasize strength development more than speed development. This might be the case early in the year or with individuals who are particularly weak.
2. When I want to induce a potentiation effect. High intensity low volume lifting prior to a speed session can help to "prime" the nervous system for the speed session and actually produce greater speed session performances than if it were not done. This should be used sparingly though and should be considered an advanced technique for more experienced athletes.