diff --git a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/VariantCallContext.java b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/VariantCallContext.java
index 16dac6fbe..8153d9b11 100755
--- a/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/VariantCallContext.java
+++ b/java/src/org/broadinstitute/sting/gatk/walkers/genotyper/VariantCallContext.java
@@ -64,4 +64,26 @@ public class VariantCallContext extends VariantContext {
     public void setRefBase(byte ref) {
         this.refBase = ref;
     }
+
+    /* these methods are only implemented for GENOTYPE_GIVEN_ALLELES MODE */
+    //todo -- expand these methods to all modes
+
+    /**
+     *
+     * @param callConfidenceThreshold the Unified Argument Collection STANDARD_CONFIDENCE_FOR_CALLING
+     * @return true if call was confidently ref
+     */
+    public boolean isCalledRef(double callConfidenceThreshold) {
+        return (confidentlyCalled && (getPhredScaledQual() < callConfidenceThreshold));
+    }
+
+    /**
+     *
+     * @param callConfidenceThreshold the Unified Argument Collection STANDARD_CONFIDENCE_FOR_CALLING
+     * @return true if call was confidently alt
+     */
+    public boolean isCalledAlt(double callConfidenceThreshold) {
+        return (confidentlyCalled && (getPhredScaledQual() > callConfidenceThreshold));
+    }
+
 }
\ No newline at end of file
diff --git a/java/src/org/broadinstitute/sting/playground/gatk/walkers/GenotypeAndValidateWalker.java b/java/src/org/broadinstitute/sting/playground/gatk/walkers/GenotypeAndValidateWalker.java
index e2a0e4847..145228f71 100755
--- a/java/src/org/broadinstitute/sting/playground/gatk/walkers/GenotypeAndValidateWalker.java
+++ b/java/src/org/broadinstitute/sting/playground/gatk/walkers/GenotypeAndValidateWalker.java
@@ -25,6 +25,8 @@
 
 package org.broadinstitute.sting.playground.gatk.walkers;
 
+import org.broad.tribble.util.variantcontext.Allele;
+import org.broad.tribble.util.variantcontext.Genotype;
 import org.broad.tribble.util.variantcontext.MutableVariantContext;
 import org.broad.tribble.util.variantcontext.VariantContext;
 import org.broad.tribble.vcf.VCFHeader;
@@ -66,11 +68,14 @@ import static org.broadinstitute.sting.utils.IndelUtils.isInsideExtendedIndel;
 @Reference(window=@Window(start=-200,stop=200))
 
 
-public class GenotypeAndValidateWalker extends RodWalker<GenotypeAndValidateWalker.CountedData, GenotypeAndValidateWalker.CountedData> {
+public class GenotypeAndValidateWalker extends RodWalker<GenotypeAndValidateWalker.CountedData, GenotypeAndValidateWalker.CountedData> implements TreeReducible<GenotypeAndValidateWalker.CountedData> {
 
-    @Output(doc="File to which validated variants should be written", required=true)
+    @Output(doc="File to which validated variants should be written", required=false)
     protected VCFWriter vcfWriter = null;
 
+    @Argument(fullName ="set_bam_truth", shortName ="bt", doc="Use the calls on the reads (bam file) as the truth dataset and validate the calls on the VCF", required=false)
+    private boolean bamIsTruth = false;
+
     @Argument(fullName="minimum_base_quality_score", shortName="mbq", doc="Minimum base quality score for calling a genotype", required=false)
     private int mbq = -1;
 
@@ -86,32 +91,35 @@ public class GenotypeAndValidateWalker extends RodWalker<GenotypeAndValidateWalk
     @Argument(fullName="condition_on_depth", shortName="depth", doc="Condition validation on a minimum depth of coverage by the reads", required=false)
     private int minDepth = -1;
 
+    @Argument(fullName ="sample", shortName ="sn", doc="Name of the sample to validate (in case your VCF/BAM has more than one sample)", required=false)
+    private String sample = "";
+
+
+
 
     private String compName = "alleles";
     private UnifiedGenotyperEngine snpEngine;
     private UnifiedGenotyperEngine indelEngine;
 
     public static class CountedData {
-        private long numTP = 0L;
-        private long numTN = 0L;
-        private long numFP = 0L;
-        private long numFN = 0L;
-        private long numUncovered = 0L;
-        private long numConfidentCalls = 0L;
-        private long numNotConfidentCalls = 0L;
+        private long nAltCalledAlt = 0L;
+        private long nAltCalledRef = 0L;
+        private long nRefCalledAlt = 0L;
+        private long nRefCalledRef = 0L;
+        private long nNotConfidentCalls = 0L;
+        private long nUncovered = 0L;
 
         /**
          * Adds the values of other to this, returning this
          * @param other the other object
          */
         public void add(CountedData other) {
-            numTP += other.numTP;
-            numTN += other.numTN;
-            numFP += other.numFP;
-            numFN += other.numFN;
-            numUncovered += other.numUncovered;
-            numNotConfidentCalls += other.numNotConfidentCalls;
-            numConfidentCalls    += other.numConfidentCalls;
+            nAltCalledAlt += other.nAltCalledAlt;
+            nAltCalledRef += other.nAltCalledRef;
+            nRefCalledAlt += other.nRefCalledAlt;
+            nRefCalledRef += other.nRefCalledRef;
+            nUncovered += other.nUncovered;
+            nNotConfidentCalls += other.nNotConfidentCalls;
         }
     }
 
@@ -133,28 +141,31 @@ public class GenotypeAndValidateWalker extends RodWalker<GenotypeAndValidateWalk
 
 
         // Initialize VCF header
-        Map<String, VCFHeader> header = VCFUtils.getVCFHeadersFromRodPrefix(getToolkit(), compName);
-        Set<String> samples = SampleUtils.getSampleList(header, VariantContextUtils.GenotypeMergeType.REQUIRE_UNIQUE);
-        Set<VCFHeaderLine> headerLines = VCFUtils.smartMergeHeaders(header.values(), logger);
-        headerLines.add(new VCFHeaderLine("source", "GenotypeAndValidate"));
-        vcfWriter.writeHeader(new VCFHeader(headerLines, samples));
-
+        if (vcfWriter != null) {
+            Map<String, VCFHeader> header = VCFUtils.getVCFHeadersFromRodPrefix(getToolkit(), compName);
+            Set<String> samples = SampleUtils.getSampleList(header, VariantContextUtils.GenotypeMergeType.REQUIRE_UNIQUE);
+            Set<VCFHeaderLine> headerLines = VCFUtils.smartMergeHeaders(header.values(), logger);
+            headerLines.add(new VCFHeaderLine("source", "GenotypeAndValidate"));
+            vcfWriter.writeHeader(new VCFHeader(headerLines, samples));
+        }
 
         // Filling in SNP calling arguments for UG
         UnifiedArgumentCollection uac = new UnifiedArgumentCollection();
         uac.OutputMode = UnifiedGenotyperEngine.OUTPUT_MODE.EMIT_ALL_SITES;
-        uac.GenotypingMode = GenotypeLikelihoodsCalculationModel.GENOTYPING_MODE.GENOTYPE_GIVEN_ALLELES;
+        if (!bamIsTruth) uac.GenotypingMode = GenotypeLikelihoodsCalculationModel.GENOTYPING_MODE.GENOTYPE_GIVEN_ALLELES;
         if (mbq >= 0) uac.MIN_BASE_QUALTY_SCORE = mbq;
         if (deletions >= 0) uac.MAX_DELETION_FRACTION = deletions;
-        if (callConf >= 0) uac.STANDARD_CONFIDENCE_FOR_CALLING = callConf;
         if (emitConf >= 0) uac.STANDARD_CONFIDENCE_FOR_EMITTING = emitConf;
-
+        if (callConf >= 0) uac.STANDARD_CONFIDENCE_FOR_CALLING = callConf;
 
         snpEngine = new UnifiedGenotyperEngine(getToolkit(), uac);
 
         // Adding the INDEL calling arguments for UG
         uac.GLmodel = GenotypeLikelihoodsCalculationModel.Model.DINDEL;
         indelEngine = new UnifiedGenotyperEngine(getToolkit(), uac);
+
+        // make sure we have callConf set to the threshold set by the UAC so we can use it later.
+        callConf = uac.STANDARD_CONFIDENCE_FOR_CALLING;
     }
 
     //---------------------------------------------------------------------------------------------------------------
@@ -181,47 +192,74 @@ public class GenotypeAndValidateWalker extends RodWalker<GenotypeAndValidateWalk
 
         // Do not operate on variants that are not covered to the optional minimum depth
         if (!context.hasReads() || (minDepth > 0 && context.getBasePileup().getBases().length < minDepth)) {
-            counter.numUncovered = 1L;
+            counter.nUncovered = 1L;
             return counter;
         }
 
-        if (!vcComp.hasAttribute("GV"))
-            throw new UserException.BadInput("Variant has no GV annotation in the INFO field. " + vcComp.getChr() + ":" + vcComp.getStart());
-
         VariantCallContext call;
         if ( vcComp.isSNP() )
             call = snpEngine.calculateLikelihoodsAndGenotypes(tracker, ref, context);
         else if ( vcComp.isIndel() ) {
             call = indelEngine.calculateLikelihoodsAndGenotypes(tracker, ref, context);
-//            if (call.vc == null) // variant context will be null on an extended indel event and I just want to call it one event.
-//                return counter;
         }
         else {
             logger.info("Not SNP or INDEL " + vcComp.getChr() + ":" + vcComp.getStart() + " " + vcComp.getAlleles());
             return counter;
         }
 
-        if (!call.confidentlyCalled) {
-            counter.numNotConfidentCalls = 1L;
-            if (vcComp.getAttribute("GV").equals("T"))
-                counter.numFN = 1L;
-            else
-                counter.numTN = 1L;
+        if (bamIsTruth) {
+            if (call.confidentlyCalled) {
+                // If truth is a confident REF call
+                if (call.isVariant()) {
+                    if (vcComp.isVariant())
+                        counter.nAltCalledAlt = 1L;  // todo -- may wanna check if the alts called are the same?
+                    else
+                        counter.nAltCalledRef = 1L;
+                }
+                // If truth is a confident ALT call
+                else {
+                    if (vcComp.isVariant())
+                        counter.nRefCalledAlt = 1L;
+                    else
+                        counter.nRefCalledRef = 1L;
+                }
+            }
+            else {
+                counter.nNotConfidentCalls = 1L;
+            }
         }
         else {
-            counter.numConfidentCalls = 1L;
-            if (vcComp.getAttribute("GV").equals("T"))
-                counter.numTP = 1L;
+            if (!vcComp.hasAttribute("GV"))
+                throw new UserException.BadInput("Variant has no GV annotation in the INFO field. " + vcComp.getChr() + ":" + vcComp.getStart());
+
+
+
+            if (call.isCalledAlt(callConf)) {
+                if (vcComp.getAttribute("GV").equals("T"))
+                    counter.nAltCalledAlt = 1L;
+                else
+                    counter.nRefCalledAlt = 1L;
+            }
+            else if (call.isCalledRef(callConf)) {
+                if (vcComp.getAttribute("GV").equals("T"))
+                    counter.nAltCalledRef = 1L;
+                else
+                    counter.nRefCalledRef = 1L;
+            }
+            else {
+                counter.nNotConfidentCalls = 1L;
+            }
+        }
+
+        if (vcfWriter != null) {
+            if (!vcComp.hasAttribute("callStatus")) {
+                MutableVariantContext mvc = new MutableVariantContext(vcComp);
+                mvc.putAttribute("callStatus", call.isCalledAlt(callConf) ? "ALT" : "REF" );
+                vcfWriter.add(mvc, ref.getBase());
+            }
             else
-                counter.numFP = 1L;
+                vcfWriter.add(vcComp, ref.getBase());
         }
-        if (!vcComp.hasAttribute("callStatus")) {
-            MutableVariantContext mvc = new MutableVariantContext(vcComp);
-            mvc.putAttribute("callStatus", call.confidentlyCalled ? "confident" : "notConfident" );
-            vcfWriter.add(mvc, ref.getBase());
-        }
-        else
-            vcfWriter.add(vcComp, ref.getBase());
         return counter;
     }
 
@@ -235,17 +273,22 @@ public class GenotypeAndValidateWalker extends RodWalker<GenotypeAndValidateWalk
         return new CountedData();
     }
 
+    public CountedData treeReduce( final CountedData sum1, final CountedData sum2) {
+        sum2.add(sum1);
+        return sum2;
+    }
+
     public CountedData reduce( final CountedData mapValue, final CountedData reduceSum ) {
         reduceSum.add(mapValue);
         return reduceSum;
     }
 
     public void onTraversalDone( CountedData reduceSum ) {
-        double ppv = 100 * ((double) reduceSum.numTP /( reduceSum.numTP + reduceSum.numFP));
-        double npv = 100 * ((double) reduceSum.numTN /( reduceSum.numTN + reduceSum.numFN));
+        double ppv = 100 * ((double) reduceSum.nAltCalledAlt /( reduceSum.nAltCalledAlt + reduceSum.nRefCalledAlt));
+        double npv = 100 * ((double) reduceSum.nRefCalledRef /( reduceSum.nRefCalledRef + reduceSum.nAltCalledRef));
         logger.info(String.format("Resulting Truth Table Output\n\n" +
                                   "---------------------------------------------------\n" +
-                                  "\t\t|\tT\t|\tF\t\n"  +
+                                  "\t\t|\tALT\t|\tREF\t\n"  +
                                   "---------------------------------------------------\n" +
                                   "called alt\t|\t%d\t|\t%d\n" +
                                   "called ref\t|\t%d\t|\t%d\n" +
@@ -253,20 +296,8 @@ public class GenotypeAndValidateWalker extends RodWalker<GenotypeAndValidateWalk
                                   "positive predictive value: %f%%\n" +
                                   "negative predictive value: %f%%\n" +
                                   "---------------------------------------------------\n" +
-                                  "uncovered: %d\n" +
-                                  "---------------------------------------------------\n", reduceSum.numTP, reduceSum.numFP, reduceSum.numFN, reduceSum.numTN, ppv, npv, reduceSum.numUncovered));
-
-        /*
-
-        logger.info("called / true      = " + reduceSum.numTP);
-        logger.info("not called / false = " + reduceSum.numTN);
-        logger.info("called /false      = " + reduceSum.numFP);
-        logger.info("not called / true = " + reduceSum.numFN);
-        logger.info("PPV = " + 100 * ((double) reduceSum.numTP /( reduceSum.numTP + reduceSum.numFP)) + "%");
-        logger.info("NPV = " + 100 * ((double) reduceSum.numTN /( reduceSum.numTN + reduceSum.numFN)) + "%");
-        logger.info("confidently called = " + reduceSum.numConfidentCalls);
-        logger.info("not confidently called = " + reduceSum.numNotConfidentCalls );
-        logger.info("Uncovered = " + reduceSum.numUncovered);
-        */
+                                  "not confident: %d\n" +
+                                  "not covered: %d\n" +
+                                  "---------------------------------------------------\n", reduceSum.nAltCalledAlt, reduceSum.nRefCalledAlt, reduceSum.nAltCalledRef, reduceSum.nRefCalledRef, ppv, npv, reduceSum.nNotConfidentCalls, reduceSum.nUncovered));
     }
 }
diff --git a/scala/qscript/oneoffs/carneiro/dataProcessingV2.scala b/scala/qscript/oneoffs/carneiro/dataProcessingV2.scala
index 7d85152a7..fd4876246 100755
--- a/scala/qscript/oneoffs/carneiro/dataProcessingV2.scala
+++ b/scala/qscript/oneoffs/carneiro/dataProcessingV2.scala
@@ -7,6 +7,7 @@ import org.broadinstitute.sting.queue.function.ListWriterFunction
 
 import net.sf.samtools.{SAMFileReader,SAMFileHeader,SAMReadGroupRecord}
 import collection.JavaConversions._
+import org.broadinstitute.sting.commandline.ArgumentSource
 
 
 class dataProcessingV2 extends QScript {
@@ -27,6 +28,9 @@ class dataProcessingV2 extends QScript {
   @Input(doc="path to R resources folder inside the Sting repository", shortName="r", required=true)
   var R: String = _
 
+  @Input(doc="The path to the binary of bwa (usually BAM files have already been mapped - but if you want to remap this is the option)", shortName="bwa", required=false)
+  var bwaPath: File = _
+
   @Input(doc="input BAM file - or list of BAM files", shortName="i", required=true)
   var input: File = _
 
@@ -57,24 +61,42 @@ class dataProcessingV2 extends QScript {
   @Input(doc="output bams at intervals only", shortName="intervals", required=false)
   var intervals: File = _
 
+  // Gracefully hide Queue's output
   val queueLogDir: String = ".qlog/"
 
+  // Use the number of contigs for scatter gathering jobs
+  var nContigs: Int = -1
 
-  def script = {
 
-    // Helpful variables
+  // Updates and checks that all input files have the same number of contigs
+  // we use the number of contigs for scatter gather.
+  def updateNumberOfContigs(n: Int): Boolean = {
+    if (nContigs < 0) {
+      nContigs = n
+      return true
+    }
+    return nContigs == n
+  }
+
+  def createSampleFiles(): Map[String, File] = {
     val outName: String         = qscript.outputDir + qscript.projectName
-    
 
-
-    //todo -- process bam headers to compile bamLists of samples.
-    var sampleTable = scala.collection.mutable.Map.empty[String, List[File]]
+    // Creating a table with SAMPLE information from each input BAM file
+    val sampleTable = scala.collection.mutable.Map.empty[String, List[File]]
     for (bam <- scala.io.Source.fromFile(input).getLines) {
       val bamFile = new File(bam)
       val samReader = new SAMFileReader(bamFile)
       val header = samReader.getFileHeader()
-      val readGroup = header.getReadGroups()
-      for (rg <- readGroup) {
+      // keep a record of the number of contigs in this bam file (they should all be the same
+      assert(updateNumberOfContigs(header.getSequenceDictionary.getSequences.size()), "Input BAMS should all have the same number of contigs. " + bam + " has " + header.getSequenceDictionary.getSequences.size())
+      val readGroups = header.getReadGroups()
+
+      // only allow one sample per file. Bam files with multiple samples would require pre-processing of the file
+      // with PrintReads to separate the samples. Tell user to do it himself!
+      assert(hasMultipleSamples(readGroups), "The pipeline requires that only one sample is present in a BAM file. Please separate the samples in " + bam)
+
+      // Fill out the sample table with the readgroups in this file
+      for (rg <- readGroups) {
         val sample = rg.getSample()
         if (!sampleTable.contains(sample))
           sampleTable(sample) = List(bamFile)
@@ -83,22 +105,36 @@ class dataProcessingV2 extends QScript {
       }
     }
 
+    // Creating one file for each sample in the dataset
     val sampleBamFiles = scala.collection.mutable.Map.empty[String, File]
-
     for ((sample, flist) <- sampleTable) {
       val sampleFileName = new File(outName + "." + sample + ".bam")
       sampleBamFiles(sample) = sampleFileName
       add(joinBams(flist, sampleFileName))
     }
+    return sampleBamFiles.toMap
+  }
 
-    println("\nFound the following samples (files created as necessary): ")
+
+  def script = {
+
+    //todo -- (option - BWA) run BWA on each bam file (per lane bam file) before performing per sample processing
+
+
+    var cohortList: List[File] = List()
+    val sampleBamFiles = createSampleFiles()
+
+    // Simple progress report
+    println("\nFound the following samples: ")
     for ((sample, file) <- sampleBamFiles)
       println("\t" + sample + " -> " + file)
 
-    val globalIntervals = new File(outName + ".intervals")
+    // If this is a 'knowns only' indel realignment run, do it only once for all samples.
+    val globalIntervals = new File(outputDir + projectName + ".intervals")
     if (knownsOnly)
       add(target(null, globalIntervals))
 
+    // Put each sample through the pipeline
     for ((sample, bam) <- sampleBamFiles) {
 
       // BAM files generated by the pipeline
@@ -124,7 +160,13 @@ class dataProcessingV2 extends QScript {
           cov(recalBam, postRecalFile),
           analyzeCovariates(preRecalFile, preOutPath),
           analyzeCovariates(postRecalFile, postOutPath))
+
+      cohortList :+= recalBam
     }
+
+    // output a BAM list with all the processed per sample files
+    val cohortFile = new File(qscript.outputDir + qscript.projectName + ".cohort.list")
+    add(writeList(cohortList, cohortFile))
   }
 
   // General arguments to all programs
@@ -142,9 +184,9 @@ class dataProcessingV2 extends QScript {
     override def inputBams = join
     override def outputBam = joined
     override def commandLine = super.commandLine + " CREATE_INDEX=true"
-    this.memoryLimit = Some(6)
     this.jarFile = qscript.mergeBamJar
     this.isIntermediate = true
+    this.analysisName = queueLogDir + outBam + ".joinBams"
     this.jobName = queueLogDir + outBam + ".joinBams"
   }
 
@@ -155,6 +197,8 @@ class dataProcessingV2 extends QScript {
     this.mismatchFraction = Some(0.0)
     this.rodBind :+= RodBind("dbsnp", "VCF", dbSNP)
     this.rodBind :+= RodBind("indels", "VCF", indels)
+    this.scatterCount = nContigs
+    this.analysisName = queueLogDir + outIntervals + ".target"
     this.jobName = queueLogDir + outIntervals + ".target"
   }
 
@@ -168,6 +212,8 @@ class dataProcessingV2 extends QScript {
     this.doNotUseSW = useSW
     this.compress = Some(0)
     this.U = Some(org.broadinstitute.sting.gatk.arguments.ValidationExclusion.TYPE.NO_READ_ORDER_VERIFICATION)  // todo -- update this with the last consensus between Tim, Matt and Eric. This is ugly!
+    this.scatterCount = nContigs
+    this.analysisName = queueLogDir + outBam + ".clean"
     this.jobName = queueLogDir + outBam + ".clean"
   }
 
@@ -182,15 +228,17 @@ class dataProcessingV2 extends QScript {
     sortOrder = null
     this.memoryLimit = Some(6)
     this.jarFile = qscript.dedupJar
-    this.isIntermediate = true
+    this.analysisName = queueLogDir + outBam + ".dedup"
     this.jobName = queueLogDir + outBam + ".dedup"
   }
 
+  //todo -- add scatter gather capability (waiting for khalid's modifications to the queue base
   case class cov (inBam: File, outRecalFile: File) extends CountCovariates with CommandLineGATKArgs {
     this.rodBind :+= RodBind("dbsnp", "VCF", dbSNP)
     this.covariate ++= List("ReadGroupCovariate", "QualityScoreCovariate", "CycleCovariate", "DinucCovariate")
     this.input_file :+= inBam
     this.recal_file = outRecalFile
+    this.analysisName = queueLogDir + outRecalFile + ".covariates"
     this.jobName = queueLogDir + outRecalFile + ".covariates"
   }
 
@@ -204,7 +252,9 @@ class dataProcessingV2 extends QScript {
     else if (qscript.intervals != null) this.intervals :+= qscript.intervals
     this.U = Some(org.broadinstitute.sting.gatk.arguments.ValidationExclusion.TYPE.NO_READ_ORDER_VERIFICATION)  // todo -- update this with the last consensus between Tim, Matt and Eric. This is ugly!
     this.index_output_bam_on_the_fly = Some(true)
+    this.analysisName = queueLogDir + outBam + ".recalibration"
     this.jobName = queueLogDir + outBam + ".recalibration"
+
   }
 
   case class analyzeCovariates (inRecalFile: File, outPath: File) extends AnalyzeCovariates {
@@ -212,12 +262,16 @@ class dataProcessingV2 extends QScript {
     this.resources = qscript.R
     this.recal_file = inRecalFile
     this.output_dir = outPath.toString
+    this.analysisName = queueLogDir + inRecalFile + ".analyze_covariates"
     this.jobName = queueLogDir + inRecalFile + ".analyze_covariates"
   }
 
   case class writeList(inBams: List[File], outBamList: File) extends ListWriterFunction {
     this.inputFiles = inBams
     this.listFile = outBamList
+    this.analysisName = queueLogDir + outBamList + ".bamList"
     this.jobName = queueLogDir + outBamList + ".bamList"
   }
+
+
 }