In Mixed Stain mode Grape performs statistical analysis of samples that contain DNA of more than 1 contributor. Such cases arise in various situations but most typically in rape cases. That's why Grape provides two different user interfaces: the first one is specifically designed for rape cases and the second one covers the general case. To access both interfaces click Setup Case button in the main window of Grape and make your choice



The Typical Rape Case button activates the following dialog



It is assumed that the evidentiary sample contains DNA of several criminals and optionally the DNA of the victim. One suspect is known, others are unknown. The number of criminals can be specified exactly or left unknown (which is possible if, for example, the victim is dead). If more than one option exist Grape chooses the possibility that favors suspect the most (e.g. having the smallest value of the likelihood ratio) and shows the result in the main window. Besides numerical results Grape can also display the formulae used for calculations. To activate this feature check the "Show symbolic output" box.

As in the Simple Case Mode the default names "Evidentiary Sample", "Suspect", "Victim" can be changed to accomodate user's preferences.

General Case interface supports the approach described, for example, in Evett I.W., Weir B.S. Interpreting DNA Evidence, Sinauer Associates, MA, USA, 1998, Chapter 7. In the dialog below you can enter names of typed persons and mark them as contributors or noncontributors according to the two concurrent hypotheses Hp and Hd. Additionally, you can specify the number of unknown contributors in the right part of the dialog.




A typical rape case can be investigated with the use of this general interface as well but it is better to use special dialog as it is more convenient.

Steps needed to setup genotypes are the same as in the
Simple Case Mode : first of all  Select Loci  that you will use in your calculations, then Set Genotypes of all persons. Optionally you can change coancestry coefficient using Choose Θ button and enter additional information through Case Info dialog.

Below is an example of Grape's main window for typical rape scenario.




We assume that the evidentiary sample Sample #145 contains DNA of 1 or 2 criminals and it is known for sure that the victim also contributes to the evidentiary sample. One suspect John Rich is typed.  Under hypothesis  Hp he is one of the criminals, under hypothesis Hd he is innocent.

Click "Calculate" to get the result



Grape considered two possible options: if number of criminals is equal to 1 or 2 and found out that the options with minimal likelihood ratio corresponds to 2 criminals. The result is shown for this option. Result includes the likelihood ratios and match probabilities for each loci as well as total values. Additionally if the check box "Show symbolic output" was selected you can see in a separate resizable window the formulae used. In the considered example it looks like as follows




As in the Simple Case Mode the case can be saved in a file or in an embedded database.  The last possibility can be quite useful for unresolved crimes. Let us assume in the example above that no suspects are identified so far. Define genotype of the suspect as 'Unknown' in the Set Genotypes dialog. It is clearly meaningless to perform any calculations in such situation (the resulting likelihood ratio is 1 for every locus). But it is still can be useful to save this case into a database. In fact when Grape is saving a case it generates automatically the possible genotype of the perpetrator of the crime and saves it as well. For mixed stains this genotype is usually not defined in a unique way and Grape saves all possibilities. This feature can be very useful: for example, you can compare that database with a database of previously convicted sexual offenders to find matches (see Database Operations Mode). Or if that database contains information of all (even unresolved) rape cases it can be searched to find matches and hence find serial crimes.