Whip cream, dissolve the gelatin and sugar in lemon juice on low heat (if you can't get unflavoured gelatin, use a packet of lemon Jell-O and skip the lemon juice and sugar, prepare the Jell-O according to instructions on the box. This won't work with the instant Jell-O kind, just with the type you have to cook). In a bowl, combine sour cream and yogurt. Stir in slightly cooled gelatin mixture, then fold in whipped cream. Refrigerate for at least 2 hours before serving. Puree half of the raspberries to make a smooth sauce, serve mousse with raspberries and sauce.