Pick over fresh raspberries and place in a mixing basin. Sprinkle with the sugar. Separate frozen raspberries and set aside until thawed.
Measure the water into a small saucepan and sprinkle over the gelatine. Set aside to soak for 5 minutes. Place over a low heat and warm until the gelatine has dissolved, then draw the pan off the heat.
Sieve the raspberries along with the juic