diff --git a/beacon_chain/logtrace.nim b/beacon_chain/logtrace.nim
index 62e8e8d54..1d1f5718d 100644
--- a/beacon_chain/logtrace.nim
+++ b/beacon_chain/logtrace.nim
@@ -5,6 +5,7 @@
 #   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 import confutils, json, times, streams, os, strutils, options, chronicles
+import json_serialization
 
 const
   LogTraceName* = "Beacon-Chain LogTrace Tool"
@@ -21,7 +22,7 @@ const
 
 type
   StartUpCommand* {.pure.} = enum
-    pubsub
+    pubsub, attest
 
   LogTraceConf* = object
     logFiles* {.
@@ -37,16 +38,73 @@ type
     case cmd* {.command.}: StartUpCommand
     of pubsub:
       discard
+    of attest:
+      discard
 
   GossipDirection* = enum
     None, Incoming, Outgoing
 
+  LogMessage* = object of RootObj
+    level* {.serializedFieldName: "lvl" .}: string
+    timestamp* {.serializedFieldName: "ts" .}: DateTime
+    msg*: string
+    topics*: string
+    tid*: int
+
+  SlotStartMessage* = object of LogMessage
+    beaconTime*: uint64
+    finalizedEpoch*: uint64
+    finalizedRoot*: string
+    finalizedSlot*: uint64
+    headEpoch*: uint64
+    headRoot*: string
+    headSlot*: uint64
+    lastSlot*: uint64
+    peers*: uint64
+    scheduledSlot*: uint64
+
+  AttestationDataObject* = object
+    slot*: uint64
+    index*: uint64
+    beaconBlockRoot* {.serializedFieldName: "beacon_block_root".}: string
+    sourceEpoch* {.serializedFieldName: "source_epoch".}: uint64
+    sourceRoot* {.serializedFieldName: "source_root".}: string
+    targetEpoch* {.serializedFieldName: "target_epoch".}: uint64
+    targetRoot* {.serializedFieldName: "target_root".}: string
+
+  AttestationObject* = object
+    aggregationBits* {.serializedFieldName: "aggregation_bits".}: string
+    data*: AttestationDataObject
+    signature*: string
+
+  AttestationSentMessage* = object of LogMessage
+    attestation*: AttestationObject
+    indexInCommittee*: uint64
+    validator*: string
+
   GossipMessage* = object
     kind*: GossipDirection
     id*: string
     datetime*: DateTime
     processed*: bool
 
+  SaMessageType* = enum
+    AttestationSent, SlotStart
+
+  SlotAttMessage* = object
+    case kind*: SaMessageType
+    of SaMessageType.AttestationSent:
+      asmsg*: AttestationSentMessage
+    of SaMessageType.SlotStart:
+      ssmsg*: SlotStartMessage
+
+proc readValue*(reader: var JsonReader, value: var DateTime) =
+  let s = reader.readValue(string)
+  try:
+    value = parse(s, "YYYY-MM-dd HH:mm:sszzz")
+  except CatchableError:
+    raiseUnexpectedValue(reader, "Invalid date time")
+
 proc init(t: typedesc[GossipMessage], kind: GossipDirection, id,
           datestr: string): GossipMessage =
   result = GossipMessage(kind: kind, id: id,
@@ -70,6 +128,41 @@ proc readLogFile(file: string): seq[JsonNode] =
   finally:
     stream.close()
 
+proc readLogFileForAttsMessages(file: string): seq[SlotAttMessage] =
+  var res = newSeq[SlotAttMessage]()
+  var stream = newFileStream(file)
+  var line: string
+  var counter = 0
+  try:
+    while not(stream.atEnd()):
+      line = stream.readLine()
+      let m = Json.decode(line, LogMessage, forwardCompatible = true)
+      if m.msg == "Attestation sent":
+        let am = Json.decode(line, AttestationSentMessage,
+                             forwardCompatible = true)
+        let m = SlotAttMessage(kind: SaMessageType.AttestationSent,
+                               asmsg: am)
+        res.add(m)
+      elif m.msg == "Slot start":
+        let sm = Json.decode(line, SlotStartMessage,
+                             forwardCompatible = true)
+        let m = SlotAttMessage(kind: SaMessageType.SlotStart,
+                               ssmsg: sm)
+        res.add(m)
+      inc(counter)
+      if counter mod 10_000 == 0:
+         info "Processing file", file = file, lines_processed = counter,
+                                 lines_filtered = len(res)
+    result = res
+
+  except SerializationError as exc:
+    error "Serialization error while reading data from file", file = file,
+          errorMsg = exc.formatMsg(line)
+  except CatchableError as exc:
+    warn "Error reading data from file", file = file, errorMsg = exc.msg
+  finally:
+    stream.close()
+
 proc filterGossipMessages(log: seq[JsonNode]): seq[GossipMessage] =
   # Because of times.DateTime object we forced to turn off [ProveInit] warnings
   # You can remove this pragmas when Nim compiler or times.nim will be fixed.
@@ -160,6 +253,44 @@ proc runPubsub(logConf: LogTraceConf, logFiles: seq[string]) =
   else:
     warn "Number of missing messages found", count = $misses
 
+proc runAttSend(logConf: LogTraceConf, logFiles: seq[string]) =
+  info "Check for late `attestation sent` messages"
+  if len(logFiles) < 1:
+    error "Number of log files are not enough to process pubsub messages",
+          logs_count = len(logFiles)
+    quit(1)
+
+  let minDuration = initDuration(seconds = 4)
+  var slotMessagesCount = 0
+  var attsMessagesCount = 0
+  var lateAttsMessagesCount = 0
+
+  for item in logFiles:
+    info "Processing log file", logFile = item
+    let data = readLogFileForAttsMessages(item)
+
+    var currentSlot: Option[SlotStartMessage]
+    for item in data:
+      if item.kind == SaMessageType.SlotStart:
+        currentSlot = some(item.ssmsg)
+        inc(slotMessagesCount)
+      elif item.kind == SaMessageType.AttestationSent:
+        if currentSlot.isSome():
+          let attestationTime = currentSlot.get().timestamp -
+                                item.asmsg.timestamp
+          if attestationTime > minDuration:
+            warn "Found an attestation that was sent later than necessary",
+                 lateness = $attestationTime, slot = currentSlot.get(),
+                 attestation = item.asmsg
+            inc(lateAttsMessagesCount)
+          inc(attsMessagesCount)
+        else:
+          warn "`Attestation sent` message appears before `Start slot` message",
+               attestation = item.asmsg
+  info "Check finished", attestation_sent_messages = attsMessagesCount,
+                         slot_messages = slotMessagesCount,
+                         late_attestation_messages = lateAttsMessagesCount
+
 proc run(conf: LogTraceConf) =
   var logFiles: seq[string]
 
@@ -179,6 +310,8 @@ proc run(conf: LogTraceConf) =
 
   if conf.cmd == StartUpCommand.pubsub:
     runPubsub(conf, logFiles)
+  elif conf.cmd == StartUpCommand.attest:
+    runAttSend(conf, logFiles)
 
 when isMainModule:
   echo LogTraceHeader
diff --git a/vendor/nim-json-serialization b/vendor/nim-json-serialization
index 463a0cf1b..1cf51931f 160000
--- a/vendor/nim-json-serialization
+++ b/vendor/nim-json-serialization
@@ -1 +1 @@
-Subproject commit 463a0cf1b79f5e586b537c0ce7518e2d1ee85984
+Subproject commit 1cf51931f1037a2c44fa0912386273c01a0e0e42